PPC: [runtime] Replace COMPARE/COMPARE_STRONG with proper Object::Compare.

PPC: [runtime] Replace COMPARE/COMPARE_STRONG with proper Object::Compare.

Port 593c655a3c814277283f9fa1520d5ce59d6b019c

Original commit message:
    This removes the weird COMPARE and COMPARE_STRONG JavaScript builtins
    and replaces them with a proper C++ implementation in Object::Compare
    and appropriate wrappers Object::LessThan, Object::GreaterThan, and
    friends that are intended to be used by a true/false returning CompareIC
    in the future, as well as the interpreter.  As a short-term solution we
    provide %Compare and %Compare_Strong entry points for the current
    CompareIC that return the appropriate integer values expected by
    fullcodegen currently.

    Now the Abstract Relational Comparison is also using the correct
    ToPrimitive implementation, which properly supports @@toPrimitive.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, dstence@us.ibm.com
BUG=v8:4307
LOG=n

Committed: https://crrev.com/8975286e9b67fd07876e6da4724eca9b43e70348
Cr-Commit-Position: refs/heads/master@{#30836}

[MTBrandyberry, 2015-09-18 18:10:33]

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

[commit-bot: I haz the power, 2015-09-18 18:10:47]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1356983002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1356983002/1

[dstence, 2015-09-18 18:33:13]

lgtm

[commit-bot: I haz the power, 2015-09-18 18:36:49]

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

[commit-bot: I haz the power, 2015-09-18 18:36:50]

Dry run: This issue passed the CQ dry run.

[MTBrandyberry, 2015-09-18 18:37:24]

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

[commit-bot: I haz the power, 2015-09-18 18:37:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1356983002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1356983002/1

[commit-bot: I haz the power, 2015-09-18 18:39:10]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-18 18:39:28]

Patchset 1 (id:??) landed as
https://crrev.com/8975286e9b67fd07876e6da4724eca9b43e70348
Cr-Commit-Position: refs/heads/master@{#30836}