Improve SpiderMonkey compatibility for Map/Set/WeakMap/WeakSet
Improve SpiderMonkey compatibility for Map/Set/WeakMap/WeakSet

anba/es6draft,jugglinmike/es6draft,anba/es6draft,jugglinmike/es6draft,jugglinmike/es6draft,anba/es6draft,jugglinmike/es6draft