PPC: Experimental support for RegExp lookbehind.

PPC: Experimental support for RegExp lookbehind.

Port 906903acb558723edf5bf87581c0c37183dc6c46

R=yangguo@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=v8:4545
LOG=N

Committed: https://crrev.com/e852c49eeae9b2140978d68e2cdd7e237feb6c5b
Cr-Commit-Position: refs/heads/master@{#32056}

[MTBrandyberry, 2015-11-17 17:49:29]

The CQ bit was checked by mbrandy@us.ibm.com to run a CQ dry run

[commit-bot: I haz the power, 2015-11-17 17:49:33]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1454783002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1454783002/1

[commit-bot: I haz the power, 2015-11-17 18:22:08]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-11-17 18:22:08]

Dry run: This issue passed the CQ dry run.

[JoranSiu, 2015-11-17 19:26:19]

On 2015/11/17 18:22:08, commit-bot: I haz the power wrote:
> Dry run: This issue passed the CQ dry run.

lgtm

[MTBrandyberry, 2015-11-17 19:38:45]

The CQ bit was checked by mbrandy@us.ibm.com

[commit-bot: I haz the power, 2015-11-17 19:38:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1454783002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1454783002/1

[commit-bot: I haz the power, 2015-11-17 19:40:56]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-17 19:41:24]

Patchset 1 (id:??) landed as
https://crrev.com/e852c49eeae9b2140978d68e2cdd7e237feb6c5b
Cr-Commit-Position: refs/heads/master@{#32056}