Further improve hashing of pointers and integers.

Further improve hashing of pointers and integers.

Also make sure that the appropriate functions are inlined properly
(using V8_INLINE instead of inline to enforce it even with GCC),
and improve the HashIsOkish unittest.

TEST=unittests
R=svenpanne@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=24427

[Benedikt Meurer, 2014-10-07 07:19:52]

bmeurer@chromium.org changed reviewers:
+ svenpanne@chromium.org

[Benedikt Meurer, 2014-10-07 07:19:52]

PTAL

[Sven Panne, 2014-10-07 07:23:18]

lgtm

[Benedikt Meurer, 2014-10-07 07:39:29]

Committed patchset #4 (id:60001) manually as 24427 (presubmit successful).