PPC: [runtime] Implement %_ToLength via ToLengthStub.

PPC: [runtime] Implement %_ToLength via ToLengthStub.

Port e678a0f9a961165ab43cd1a6080fcb11995b701a

Original commit message:
    Use %_ToLength for TO_LENGTH, implemented via a ToLengthStub
    that supports a fast path for small integers. Everything else is still
    handled in the runtime.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, dstence@us.ibm.com
BUG=v8:4494
LOG=n

Committed: https://crrev.com/8fafb2916c8ef046b8e841f2fa12b46a8ac8772a
Cr-Commit-Position: refs/heads/master@{#31384}

[michael_dawson, 2015-10-19 16:26:50]

On 2015/10/19 14:45:13, mtbrandyberry wrote:

lgtm

[MTBrandyberry, 2015-10-19 16:28:07]

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

[commit-bot: I haz the power, 2015-10-19 16:28:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1412153003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1412153003/1

[michael_dawson, 2015-10-19 16:55:34]

On 2015/10/19 16:28:17, commit-bot: I haz the power wrote:
> CQ is trying da patch. Follow status at
>  https://chromium-cq-status.appspot.com/patch-status/1412153003/1
> View timeline at
>  https://chromium-cq-status.appspot.com/patch-timeline/1412153003/1

lgtm.

[commit-bot: I haz the power, 2015-10-19 17:00:36]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-19 17:01:00]

Patchset 1 (id:??) landed as
https://crrev.com/8fafb2916c8ef046b8e841f2fa12b46a8ac8772a
Cr-Commit-Position: refs/heads/master@{#31384}