Allow zero or multiple imported names.

test/module/inside_block/inside_block.wren

@@ -0,0 +1,10 @@
+var Module = "outer"
+
+if (true) {
+  import "module" for Module
+  // expect: ran module
+
+  IO.print(Module) // expect: from module
+}
+
+IO.print(Module) // expect: outer

test/module/inside_block/module.wren

@@ -0,0 +1,3 @@
+// nontest
+var Module = "from module"
+IO.print("ran module")