[es6] Iterators and generators should "extend" %IteratorPrototype%

[es6] Iterators and generators should "extend" %IteratorPrototype%

All the builtin iterators as well as the generator objects have an
object called %IteratorPrototype% in the spec between them and
%ObjectPrototype%.

BUG=v8:3568
LOG=N

Committed: https://crrev.com/834a8e9f637c175ad214a06aa6a262b73a90627d
Cr-Commit-Position: refs/heads/master@{#28426}

[arv (Not doing code reviews), 2015-05-14 22:22:52]

arv@chromium.org changed reviewers:
+ adamk@chromium.org, wingo@igalia.com

[arv (Not doing code reviews), 2015-05-14 22:22:52]

PTAL

[arv (Not doing code reviews), 2015-05-14 22:26:24]

Add missing files

[wingo, 2015-05-15 15:04:18]

lgtm

[arv (Not doing code reviews), 2015-05-15 15:07:48]

The CQ bit was checked by arv@chromium.org

[commit-bot: I haz the power, 2015-05-15 15:07:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1128233008/20001

[commit-bot: I haz the power, 2015-05-15 15:09:55]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-05-15 15:10:15]

Patchset 2 (id:??) landed as
https://crrev.com/834a8e9f637c175ad214a06aa6a262b73a90627d
Cr-Commit-Position: refs/heads/master@{#28426}