PPC: [es6] Better support for built-ins subclassing.

PPC: [es6] Better support for built-ins subclassing.

Port 4490ce85205d3504dc0bf444f5e8b3deb04cbb06

Original commit message:
    Create proper initial map for original constructor (new.target) instead of doing prototype
    transition on the base constructor's initial map. This approach fixes in-object slack tracking
    for subclass instances.
    This CL also fixes subclassing from String.

    It also fixes typed array map smashing done during typed array initialization.

R=ishell@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, dstence@us.ibm.com
BUG=v8:3101, v8:3330, v8:4419
LOG=N

Committed: https://crrev.com/5a8da4945c6342603c719059e5830b0e0ae02fc1
Cr-Commit-Position: refs/heads/master@{#31720}

[Igor Sheludko, 2015-11-02 19:27:16]

lgtm

[MTBrandyberry, 2015-11-02 19:33:27]

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

[commit-bot: I haz the power, 2015-11-02 19:33:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1425353002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1425353002/1

[commit-bot: I haz the power, 2015-11-02 19:51:54]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-02 19:52:21]

Patchset 1 (id:??) landed as
https://crrev.com/5a8da4945c6342603c719059e5830b0e0ae02fc1
Cr-Commit-Position: refs/heads/master@{#31720}