Update to latest spec.

The text now reflects @allenwb's changes per http://people.mozilla.org/~jorendorff/es6-draft.html#sec-promise-objects. Follow-up changes to resolve open issues will build upon this text so that he can make easier deltas in the official spec.
Fix typos and other insubstantial editorial issues.

This includes everything pointed out in the following ECMAScript bugs:

- https://bugs.ecmascript.org/show_bug.cgi?id=2430
- https://bugs.ecmascript.org/show_bug.cgi?id=2544
- https://bugs.ecmascript.org/show_bug.cgi?id=2556
- https://bugs.ecmascript.org/show_bug.cgi?id=2557
- https://bugs.ecmascript.org/show_bug.cgi?id=2466
Add back additions to the Well-Known Intrinsic Objects Table.

The latest ES6 spec does not have these entries, despite referring to %Promise% and %PromisePrototype% in its text.
Move constructor parameter check after `this` check.

Fixes https://bugs.ecmascript.org/show_bug.cgi?id=2482
Add missing type check in AllocatePromise.

Fixes https://bugs.ecmascript.org/show_bug.cgi?id=2478
Update reference implementation to follow new spec text.