PPC: Changes to allow AIX to compile with gcc 4.8.3

PPC: Changes to allow AIX to compile with gcc 4.8.3

We were able to remove most of our changes needed to compile
on AIX with an earlier compiler level.  These changes are the
remaining ones.

The changes in heap/heap.cc are needed because otherwise the
compiler complains that result is potentially used before
it is initialized.

The changes in heap/mark-compact.cc are required because
AIX supports the full 64 bit address range so the check
being guarded is invalid.

The changes in build/toolchain.gypi and
test/cctest/cctest/gyp are aix only and are adjust the
compile/link options to allow the AIX build to succeed.

	modified:   build/toolchain.gypi
	modified:   src/heap/heap.cc
	modified:   src/heap/mark-compact.cc
	modified:   test/cctest/cctest.gyp

R=danno@chromium.org, svenpanne@chromium.org

BUG=

Committed: https://crrev.com/8685219066d49995219328d39bbff9ea05f6a60c
Cr-Commit-Position: refs/heads/master@{#27255}

[michael_dawson, 2015-03-16 21:29:13]

Some minor changes to support compiling on AIX with gcc 4.8.3

[Sven Panne, 2015-03-17 07:19:20]

lgtm

[Sven Panne, 2015-03-18 08:07:36]

The CQ bit was checked by svenpanne@chromium.org

[commit-bot: I haz the power, 2015-03-18 08:07:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1013833002/1

[commit-bot: I haz the power, 2015-03-18 08:43:25]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-18 08:43:36]

Patchset 1 (id:??) landed as
https://crrev.com/8685219066d49995219328d39bbff9ea05f6a60c
Cr-Commit-Position: refs/heads/master@{#27255}