tcmalloc: add x32 abi support to linux_syscall_support.h

tcmalloc: add x32 abi support to linux_syscall_support.h

These enhancements are in upstream lss project.  They've been submitted
to the gperftools project as well (although not yet merged).

BUG=chromium:219015
TEST=trybots

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=193821

[willchan no longer on Chromium, 2013-04-05 04:11:19]

Markus is the expert on linux_syscall_support. Markus, can you handle this
review and then jar or I will rubberstamp it?

Please don't update vendor. That's supposed to match the upstream (gperftools)
exactly, so we can track diffs vs our chromium branch. When you actually commit
the change upstream, then we can update the vendor branch to match it.

[vapier, 2013-04-10 16:24:53]

i've dropped the vendor/ part since upstream hasn't gotten back to me yet
https://code.google.com/p/gperftools/issues/detail?id=518

as for the linux_syscall_support stuff, Markus approved these changes to the
upstream linux_syscall_support project and i've committed them there already. 
this is just backporting those changes to the tcmalloc project.

[willchan no longer on Chromium, 2013-04-10 17:48:25]

LGTM then

[vapier, 2013-04-11 22:16:19]

for reference, those trybot failures were due to bugs on the trybots themselves

CrOS was hitting that blink/V8 bug which was announced:
PSA: Build fix for V8MutationCallback compilation errors

looking at the nacl_sdk bot history, every try run on there is failing in the
exact same way for all CLs (not just mine)

[commit-bot: I haz the power, 2013-04-11 22:16:35]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/vapier@chromium.org/13648012/4001

[commit-bot: I haz the power, 2013-04-12 01:44:07]

Change committed as 193821