ES6: Add support for Map and Set Iterator

src/macros.py

Index: src/macros.py
diff --git a/src/macros.py b/src/macros.py
index 9b256cb7b961f977c584023c0760c5f90a7113e5..305a693d441f974a63fddbd9d29c2d3db02d6b9c 100644
--- a/src/macros.py
+++ b/src/macros.py
@@ -126,6 +126,8 @@ macro IS_GLOBAL(arg)            = (%_ClassOf(arg) === 'global');
 macro IS_ARRAYBUFFER(arg)       = (%_ClassOf(arg) === 'ArrayBuffer');
 macro IS_DATAVIEW(arg)          = (%_ClassOf(arg) === 'DataView');
 macro IS_GENERATOR(arg)         = (%_ClassOf(arg) === 'Generator');
+macro IS_SET_ITERATOR(arg)      = (%_ClassOf(arg) === 'Set Iterator');
+macro IS_MAP_ITERATOR(arg)      = (%_ClassOf(arg) === 'Map Iterator');
 macro IS_UNDETECTABLE(arg)      = (%_IsUndetectableObject(arg));
 macro FLOOR(arg)                = $floor(arg);