Support 64-bit reserved_at_zero value chrome-side

NaCl: Support 64-bit reserved_at_zero value

This change will make the x86-32 sandbox on Linux non-zero-based until the change at http://codereview.chromium.org/10832040/ is committed in Chromium. Also, on Atom, performance will be temporarily reduced but not broken. 

BUG=http://code.google.com/p/nativeclient/issues/detail?id=2927
TEST=trybots

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=149333

[Mark Seaborn, 2012-07-30 21:14:56]

LGTM, but as with http://codereview.chromium.org/10832040/, please add a note to
the commit message to warn that this may make the x86-32 sandbox non-zero-based
until the other change is committed (or will fix the problem, depending on the
order you commit :-) ).

[Austin Benson, 2012-07-30 22:24:41]

Message updated.  Going to commit this one first.

[commit-bot: I haz the power, 2012-07-30 22:25:40]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/arbenson@google.com/10826039/1

[commit-bot: I haz the power, 2012-07-30 22:25:42]

Presubmit check for 10826039-1 failed and returned exit status 1.

Running presubmit commit checks ...

** Presubmit ERRORS **
Missing LGTM from an OWNER for files in these directories:
    chrome

[commit-bot: I haz the power, 2012-07-31 23:07:54]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/arbenson@google.com/10826039/1

[commit-bot: I haz the power, 2012-08-01 00:36:33]

Change committed as 149333