ES6: Add support for Map and Set Iterator

src/collection.js

Index: src/collection.js
diff --git a/src/collection.js b/src/collection.js
index 3ed452eb38f02abcc031d00adb5a8dfba37aed31..0d8dd77f7bd3be944ffcd25b51544d8ebe740c00 100644
--- a/src/collection.js
+++ b/src/collection.js
@@ -79,7 +79,7 @@ function SetForEach(f, receiver) {
     throw MakeTypeError('called_non_callable', [f]);
   }
 
-  var iterator = %SetCreateIterator(this, ITERATOR_KIND_VALUES);
+  var iterator = new SetIterator(this, ITERATOR_KIND_VALUES);
   var entry;
   var stepping = %_DebugCallbackSupportsStepping(f);
   while (!(entry = %SetIteratorNext(iterator)).done) {
@@ -190,7 +190,7 @@ function MapForEach(f, receiver) {
     throw MakeTypeError('called_non_callable', [f]);
   }
 
-  var iterator = %MapCreateIterator(this, ITERATOR_KIND_ENTRIES);
+  var iterator = new MapIterator(this, ITERATOR_KIND_ENTRIES);
   var entry;
   var stepping = %_DebugCallbackSupportsStepping(f);
   while (!(entry = %MapIteratorNext(iterator)).done) {