"IO" -> "System".

Get rid of the separate opt-in IO class and replace it with a core
System class.

- Remove wren_io.c, wren_io.h, and io.wren.
- Remove the flags that disable it.
- Remove the overloads for print() with different arity. (It was an
  experiment, but I don't think it's that useful.)
- Remove IO.read(). That will reappear using libuv in the CLI at some
  point.
- Remove IO.time. Doesn't seem to have been used.
- Update all of the tests, docs, etc.

I'm sorry for all the breakage this causes, but I think "System" is a
better name for this class (it makes it natural to add things like
"System.gc()") and frees up "IO" for referring to the CLI's IO module.

test/core/list/add.wren

@@ -1,8 +1,8 @@
 var a = [1]
 a.add(2)
-IO.print(a) // expect: [1, 2]
+System.print(a) // expect: [1, 2]
 a.add(3)
-IO.print(a) // expect: [1, 2, 3]
+System.print(a) // expect: [1, 2, 3]
 
 // Returns added element.
-IO.print(a.add(4)) // expect: 4
+System.print(a.add(4)) // expect: 4

test/core/list/add_all.wren

@@ -1,11 +1,11 @@
 var a = [1]
 a.addAll([2, 3])
-IO.print(a) // expect: [1, 2, 3]
+System.print(a) // expect: [1, 2, 3]
 a.addAll([])
-IO.print(a) // expect: [1, 2, 3]
+System.print(a) // expect: [1, 2, 3]
 a.addAll(4..6)
-IO.print(a) // expect: [1, 2, 3, 4, 5, 6]
+System.print(a) // expect: [1, 2, 3, 4, 5, 6]
 
 // Returns argument.
 var range = 7..9
-IO.print(a.addAll(range) == range) // expect: true
+System.print(a.addAll(range) == range) // expect: true

test/core/list/clear.wren

@@ -1,7 +1,7 @@
 var a = [1, 2, 3]
 a.clear()
-IO.print(a)       // expect: []
-IO.print(a.count) // expect: 0
+System.print(a)       // expect: []
+System.print(a.count) // expect: 0
 
 // Returns null.
-IO.print([1, 2].clear()) // expect: null
+System.print([1, 2].clear()) // expect: null

test/core/list/contains.wren

@@ -1,6 +1,6 @@
 var list = [1, 2, 3, 4, "foo"]
 
-IO.print(list.contains(2))      // expect: true
-IO.print(list.contains(5))      // expect: false
-IO.print(list.contains("foo"))  // expect: true
-IO.print(list.contains("bar"))  // expect: false
+System.print(list.contains(2))      // expect: true
+System.print(list.contains(5))      // expect: false
+System.print(list.contains("foo"))  // expect: true
+System.print(list.contains("bar"))  // expect: false

test/core/list/count.wren

@@ -1,3 +1,3 @@
-IO.print([].count)           // expect: 0
-IO.print([1].count)          // expect: 1
-IO.print([1, 2, 3, 4].count) // expect: 4
+System.print([].count)           // expect: 0
+System.print([1].count)          // expect: 1
+System.print([1, 2, 3, 4].count) // expect: 4

test/core/list/count_predicate.wren

@@ -1,6 +1,6 @@
 var a = [1, 2, 3]
 
-IO.print(a.count {|x| x > 3 })      // expect: 0
-IO.print(a.count {|x| x > 1 })      // expect: 2
+System.print(a.count {|x| x > 3 })      // expect: 0
+System.print(a.count {|x| x > 1 })      // expect: 2
 
-IO.print([].count {|x| true })      // expect: 0
+System.print([].count {|x| true })      // expect: 0

test/core/list/count_predicate_non_bool_returning_fn.wren

@@ -1,3 +1,3 @@
 var a = [1, 2, 3]
 
-IO.print(a.count {|x| "truthy" })   // expect: 3
+System.print(a.count {|x| "truthy" })   // expect: 3

test/core/list/each.wren

@@ -1,3 +1,3 @@
 var words = ""
 ["One", "Two", "Three"].each {|word| words = words + word }
-IO.print(words) // expect: OneTwoThree
+System.print(words) // expect: OneTwoThree

test/core/list/each_no_items.wren

@@ -1,3 +1,3 @@
 var i = 0
 [].each {|item| i = i + 1 }
-IO.print(i) // expect: 0
+System.print(i) // expect: 0

test/core/list/insert.wren

@@ -1,41 +1,41 @@
 // Add to empty list.
 var a = []
 a.insert(0, 1)
-IO.print(a) // expect: [1]
+System.print(a) // expect: [1]
 
 // Normal indices.
 var b = [1, 2, 3]
 b.insert(0, 4)
-IO.print(b) // expect: [4, 1, 2, 3]
+System.print(b) // expect: [4, 1, 2, 3]
 
 var c = [1, 2, 3]
 c.insert(1, 4)
-IO.print(c) // expect: [1, 4, 2, 3]
+System.print(c) // expect: [1, 4, 2, 3]
 
 var d = [1, 2, 3]
 d.insert(2, 4)
-IO.print(d) // expect: [1, 2, 4, 3]
+System.print(d) // expect: [1, 2, 4, 3]
 
 var e = [1, 2, 3]
 e.insert(3, 4)
-IO.print(e) // expect: [1, 2, 3, 4]
+System.print(e) // expect: [1, 2, 3, 4]
 
 // Negative indices.
 var f = [1, 2, 3]
 f.insert(-4, 4)
-IO.print(f) // expect: [4, 1, 2, 3]
+System.print(f) // expect: [4, 1, 2, 3]
 
 var g = [1, 2, 3]
 g.insert(-3, 4)
-IO.print(g) // expect: [1, 4, 2, 3]
+System.print(g) // expect: [1, 4, 2, 3]
 
 var h = [1, 2, 3]
 h.insert(-2, 4)
-IO.print(h) // expect: [1, 2, 4, 3]
+System.print(h) // expect: [1, 2, 4, 3]
 
 var i = [1, 2, 3]
 i.insert(-1, 4)
-IO.print(i) // expect: [1, 2, 3, 4]
+System.print(i) // expect: [1, 2, 3, 4]
 
 // Returns.inserted value.
-IO.print([1, 2].insert(0, 3)) // expect: 3
+System.print([1, 2].insert(0, 3)) // expect: 3

test/core/list/iterate.wren

@@ -1,13 +1,13 @@
 var a = ["one", "two", "three", "four"]
-IO.print(a.iterate(null)) // expect: 0
-IO.print(a.iterate(0)) // expect: 1
-IO.print(a.iterate(1)) // expect: 2
-IO.print(a.iterate(2)) // expect: 3
-IO.print(a.iterate(3)) // expect: false
+System.print(a.iterate(null)) // expect: 0
+System.print(a.iterate(0)) // expect: 1
+System.print(a.iterate(1)) // expect: 2
+System.print(a.iterate(2)) // expect: 3
+System.print(a.iterate(3)) // expect: false
 
 // Out of bounds.
-IO.print(a.iterate(123)) // expect: false
-IO.print(a.iterate(-1)) // expect: false
+System.print(a.iterate(123)) // expect: false
+System.print(a.iterate(-1)) // expect: false
 
 // Nothing to iterate in an empty list.
-IO.print([].iterate(null)) // expect: false
+System.print([].iterate(null)) // expect: false

test/core/list/iterator_value.wren

@@ -1,5 +1,5 @@
 var a = ["one", "two", "three", "four"]
-IO.print(a.iteratorValue(0)) // expect: one
-IO.print(a.iteratorValue(1)) // expect: two
-IO.print(a.iteratorValue(2)) // expect: three
-IO.print(a.iteratorValue(3)) // expect: four
+System.print(a.iteratorValue(0)) // expect: one
+System.print(a.iteratorValue(1)) // expect: two
+System.print(a.iteratorValue(2)) // expect: three
+System.print(a.iteratorValue(3)) // expect: four

test/core/list/join.wren

@@ -1,17 +1,17 @@
 // Handle empty list.
-IO.print([].join(",") == "") // expect: true
+System.print([].join(",") == "") // expect: true
 
 // Handle a simple list with an empty delimeter.
-IO.print([1, 2, 3].join("")) // expect: 123
+System.print([1, 2, 3].join("")) // expect: 123
 
 // Handle a simple list with no separator.
-IO.print([1, 2, 3].join) // expect: 123
+System.print([1, 2, 3].join) // expect: 123
 
 // Does not quote strings.
-IO.print([1, "2", true].join(",")) // expect: 1,2,true
+System.print([1, "2", true].join(",")) // expect: 1,2,true
 
 // Nested lists.
-IO.print([1, [2, [3], 4], 5].join(",")) // expect: 1,[2, [3], 4],5
+System.print([1, [2, [3], 4], 5].join(",")) // expect: 1,[2, [3], 4],5
 
 // Calls toString on elements.
 class Foo {
@@ -19,6 +19,6 @@ class Foo {
   toString { "Foo.toString" }
 }
 
-IO.print([1, Foo.new(), 2].join(", ")) // expect: 1, Foo.toString, 2
+System.print([1, Foo.new(), 2].join(", ")) // expect: 1, Foo.toString, 2
 
 // TODO: Handle lists that contain themselves.

test/core/list/map.wren

@@ -1,3 +1,3 @@
 var a = [1, 2, 3]
 var b = a.map {|x| x + 1 }.toList
-IO.print(b) // expect: [2, 3, 4]
+System.print(b) // expect: [2, 3, 4]

test/core/list/new.wren

@@ -1,6 +1,6 @@
 var list = List.new()
 
-IO.print(list.count) // expect: 0
-IO.print(list) // expect: []
+System.print(list.count) // expect: 0
+System.print(list) // expect: []
 list.add(1)
-IO.print(list) // expect: [1]
+System.print(list) // expect: [1]

test/core/list/not.wren

@@ -1,2 +1,2 @@
-IO.print(![1, 2]) // expect: false
-IO.print(![])     // expect: false
+System.print(![1, 2]) // expect: false
+System.print(![])     // expect: false

test/core/list/plus.wren

@@ -6,13 +6,13 @@ var e = a + []
 var f = [] + a
 var g = [] + []
 
-IO.print(a) // expect: [1, 2, 3]
-IO.print(b) // expect: [4, 5, 6]
-IO.print(c) // expect: [1, 2, 3, 4, 5, 6]
-IO.print(d) // expect: [1, 2, 3, 4, 5, 6]
-IO.print(e) // expect: [1, 2, 3]
-IO.print(f) // expect: [1, 2, 3]
-IO.print(g) // expect: []
+System.print(a) // expect: [1, 2, 3]
+System.print(b) // expect: [4, 5, 6]
+System.print(c) // expect: [1, 2, 3, 4, 5, 6]
+System.print(d) // expect: [1, 2, 3, 4, 5, 6]
+System.print(e) // expect: [1, 2, 3]
+System.print(f) // expect: [1, 2, 3]
+System.print(g) // expect: []
 
 // Doesn't modify original list.
-IO.print(a) // expect: [1, 2, 3]
+System.print(a) // expect: [1, 2, 3]

test/core/list/reduce.wren

@@ -3,12 +3,12 @@ var b = ["W", "o", "r", "l", "d"]
 var max = Fn.new {|a, b| a > b ? a : b }
 var sum = Fn.new {|a, b| a + b }
 
-IO.print(a.reduce(max)) // expect: 5
-IO.print(a.reduce(10, max)) // expect: 10
+System.print(a.reduce(max)) // expect: 5
+System.print(a.reduce(10, max)) // expect: 10
 
-IO.print(a.reduce(sum)) // expect: 13
-IO.print(a.reduce(-1, sum)) // expect: 12
+System.print(a.reduce(sum)) // expect: 13
+System.print(a.reduce(-1, sum)) // expect: 12
 
 // sum also concatenates strings
-IO.print(b.reduce("Hello ", sum)) // expect: Hello World
-IO.print(b.reduce(sum)) // expect: World
+System.print(b.reduce("Hello ", sum)) // expect: Hello World
+System.print(b.reduce(sum)) // expect: World

test/core/list/reduce_single_item.wren

@@ -1,2 +1,2 @@
-IO.print([1].reduce {|a, b| 42 }) // expect: 1
-IO.print([].reduce(1) {|a, b| 42 }) // expect: 1
+System.print([1].reduce {|a, b| 42 }) // expect: 1
+System.print([].reduce(1) {|a, b| 42 }) // expect: 1

test/core/list/remove_at.wren

@@ -1,27 +1,27 @@
 var a = [1, 2, 3]
 a.removeAt(0)
-IO.print(a) // expect: [2, 3]
+System.print(a) // expect: [2, 3]
 
 var b = [1, 2, 3]
 b.removeAt(1)
-IO.print(b) // expect: [1, 3]
+System.print(b) // expect: [1, 3]
 
 var c = [1, 2, 3]
 c.removeAt(2)
-IO.print(c) // expect: [1, 2]
+System.print(c) // expect: [1, 2]
 
 // Index backwards from end.
 var d = [1, 2, 3]
 d.removeAt(-3)
-IO.print(d) // expect: [2, 3]
+System.print(d) // expect: [2, 3]
 
 var e = [1, 2, 3]
 e.removeAt(-2)
-IO.print(e) // expect: [1, 3]
+System.print(e) // expect: [1, 3]
 
 var f = [1, 2, 3]
 f.removeAt(-1)
-IO.print(f) // expect: [1, 2]
+System.print(f) // expect: [1, 2]
 
 // Return the removed value.
-IO.print([3, 4, 5].removeAt(1)) // expect: 4
+System.print([3, 4, 5].removeAt(1)) // expect: 4

test/core/list/subscript.wren

@@ -1,12 +1,12 @@
 // Returns elements.
 var list = ["a", "b", "c", "d"]
-IO.print(list[0]) // expect: a
-IO.print(list[1]) // expect: b
-IO.print(list[2]) // expect: c
-IO.print(list[3]) // expect: d
+System.print(list[0]) // expect: a
+System.print(list[1]) // expect: b
+System.print(list[2]) // expect: c
+System.print(list[3]) // expect: d
 
 // Allows indexing backwards from the end.
-IO.print(list[-4]) // expect: a
-IO.print(list[-3]) // expect: b
-IO.print(list[-2]) // expect: c
-IO.print(list[-1]) // expect: d
+System.print(list[-4]) // expect: a
+System.print(list[-3]) // expect: b
+System.print(list[-2]) // expect: c
+System.print(list[-1]) // expect: d

test/core/list/subscript_range.wren

@@ -1,35 +1,35 @@
 // Returns lists.
 var list = ["a", "b", "c", "d", "e"]
-IO.print(list[0..0]) // expect: [a]
-IO.print(list[1...1]) // expect: []
-IO.print(list[1..2]) // expect: [b, c]
-IO.print(list[1...2]) // expect: [b]
-IO.print(list[2..4]) // expect: [c, d, e]
-IO.print(list[2...5]) // expect: [c, d, e]
+System.print(list[0..0]) // expect: [a]
+System.print(list[1...1]) // expect: []
+System.print(list[1..2]) // expect: [b, c]
+System.print(list[1...2]) // expect: [b]
+System.print(list[2..4]) // expect: [c, d, e]
+System.print(list[2...5]) // expect: [c, d, e]
 
 // A backwards range reverses.
-IO.print(list[3..1]) // expect: [d, c, b]
-IO.print(list[3...1]) // expect: [d, c]
-IO.print(list[3...3]) // expect: []
+System.print(list[3..1]) // expect: [d, c, b]
+System.print(list[3...1]) // expect: [d, c]
+System.print(list[3...3]) // expect: []
 
 // Negative ranges index from the end.
-IO.print(list[-5..-2]) // expect: [a, b, c, d]
-IO.print(list[-5...-2]) // expect: [a, b, c]
-IO.print(list[-3..-5]) // expect: [c, b, a]
-IO.print(list[-3...-6]) // expect: [c, b, a]
+System.print(list[-5..-2]) // expect: [a, b, c, d]
+System.print(list[-5...-2]) // expect: [a, b, c]
+System.print(list[-3..-5]) // expect: [c, b, a]
+System.print(list[-3...-6]) // expect: [c, b, a]
 
 // Half-negative ranges are treated like the negative value is fixed before
 // walking the range.
-IO.print(list[-5..3]) // expect: [a, b, c, d]
-IO.print(list[-3...5]) // expect: [c, d, e]
-IO.print(list[-2..1]) // expect: [d, c, b]
-IO.print(list[-2...0]) // expect: [d, c, b]
+System.print(list[-5..3]) // expect: [a, b, c, d]
+System.print(list[-3...5]) // expect: [c, d, e]
+System.print(list[-2..1]) // expect: [d, c, b]
+System.print(list[-2...0]) // expect: [d, c, b]
 
-IO.print(list[1..-2]) // expect: [b, c, d]
-IO.print(list[2...-1]) // expect: [c, d]
-IO.print(list[4..-5]) // expect: [e, d, c, b, a]
-IO.print(list[3...-6]) // expect: [d, c, b, a]
+System.print(list[1..-2]) // expect: [b, c, d]
+System.print(list[2...-1]) // expect: [c, d]
+System.print(list[4..-5]) // expect: [e, d, c, b, a]
+System.print(list[3...-6]) // expect: [d, c, b, a]
 
 // An empty range at zero is allowed on an empty list.
-IO.print([][0...0]) // expect: []
-IO.print([][0..-1]) // expect: []
+System.print([][0...0]) // expect: []
+System.print([][0..-1]) // expect: []

test/core/list/subscript_setter.wren

@@ -4,13 +4,13 @@
   list[0] = 5
   list[1] = 6
   list[2] = 7
-  IO.print(list) // expect: [5, 6, 7]
+  System.print(list) // expect: [5, 6, 7]
 }
 
 // Returns right-hand side.
 {
   var list = [1, 2, 3]
-  IO.print(list[1] = 5) // expect: 5
+  System.print(list[1] = 5) // expect: 5
 }
 
 // Negative indices.
@@ -19,5 +19,5 @@
   list[-1] = 5
   list[-2] = 6
   list[-3] = 7
-  IO.print(list) // expect: [7, 6, 5]
+  System.print(list) // expect: [7, 6, 5]
 }

test/core/list/to_string.wren

@@ -1,11 +1,11 @@
 // Handle empty list.
-IO.print([].toString)             // expect: []
+System.print([].toString)             // expect: []
 
 // Does not quote strings.
-IO.print([1, "2", true].toString) // expect: [1, 2, true]
+System.print([1, "2", true].toString) // expect: [1, 2, true]
 
 // Nested lists.
-IO.print([1, [2, [3], 4], 5]) // expect: [1, [2, [3], 4], 5]
+System.print([1, [2, [3], 4], 5]) // expect: [1, [2, [3], 4], 5]
 
 // Calls toString on elements.
 class Foo {
@@ -13,6 +13,6 @@ class Foo {
   toString { "Foo.toString" }
 }
 
-IO.print([1, Foo.new(), 2]) // expect: [1, Foo.toString, 2]
+System.print([1, Foo.new(), 2]) // expect: [1, Foo.toString, 2]
 
 // TODO: Handle lists that contain themselves.

test/core/list/type.wren

@@ -1,5 +1,5 @@
-IO.print([] is List)      // expect: true
-IO.print([] is Sequence)  // expect: true
-IO.print([] is Object)    // expect: true
-IO.print([] is Bool)      // expect: false
-IO.print([].type == List) // expect: true
+System.print([] is List)      // expect: true
+System.print([] is Sequence)  // expect: true
+System.print([] is Object)    // expect: true
+System.print([] is Bool)      // expect: false
+System.print([].type == List) // expect: true

test/core/list/where.wren

@@ -1,6 +1,6 @@
 var a = [1, 2, 3]
 var b = a.where {|x| x > 1 }.toList
-IO.print(b) // expect: [2, 3]
+System.print(b) // expect: [2, 3]
 
 var c = a.where {|x| x > 10 }.toList
-IO.print(c) // expect: []
+System.print(c) // expect: []