Fix closures in methods.

A local name inside a method should always resolve to a self send even
if there is a local variable with that name outside of the method.

test/language/variable/local_outside_method.wren

@@ -0,0 +1,22 @@
+{
+  var foo = "variable"
+
+  class Foo {
+    construct new() {}
+
+    foo { "method" }
+
+    method {
+      System.print(foo)
+    }
+
+    static foo { "class method" }
+
+    static classMethod {
+      System.print(foo)
+    }
+  }
+
+  Foo.new().method // expect: method
+  Foo.classMethod  // expect: class method
+}