Allow lookup of module exports by export name.

Allow lookup of module exports by export name.

This required fixing the exports_ hash map to use the appropriate
comparison function instead of pointer comparison.

BUG=v8:1569
LOG=n

Committed: https://crrev.com/a7840a2b3ea2db8b8bd3b80311334dbe39256ebc
Cr-Commit-Position: refs/heads/master@{#26920}

[adamk, 2015-02-27 00:33:59]

adamk@chromium.org changed reviewers:
+ rossberg@chromium.org

[arv (Not doing code reviews), 2015-02-27 02:59:56]

arv@chromium.org changed reviewers:
+ arv@chromium.org

[arv (Not doing code reviews), 2015-02-27 02:59:57]

LGTM

[adamk, 2015-02-27 17:25:14]

The CQ bit was checked by adamk@chromium.org

[commit-bot: I haz the power, 2015-02-27 17:25:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/960793003/1

[commit-bot: I haz the power, 2015-02-27 18:04:53]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-27 18:05:04]

Patchset 1 (id:??) landed as
https://crrev.com/a7840a2b3ea2db8b8bd3b80311334dbe39256ebc
Cr-Commit-Position: refs/heads/master@{#26920}