Update protobuf for 64-bit compatibility on Mac OS X

Update protobuf for 64-bit compatibility on Mac OS X.

The system's routines from <libkern/OSAtomic.h> use int64_t as their 64-bit
type. int64_t is a typedef for long long. Google's atomicops.h routines use
Atomic64 as their 64-bit type. Atomic64 is a typedef for intptr_t, which is
in turn a typedef for long. It isn't possible to cast from long* to long long*
with const_cast, reinterpret_cast is needed. This change fixes this problem
the same way Chrome fixed it in https://codereview.chromium.org/6091007 .

protobuf r423 renamed GOOGLE_PROTOBUF_HOST_ARCH_64_BIT to
GOOGLE_PROTOBUF_ARCH_64_BIT, but the change was not made in
atomicops_internals_atomicword_compat.h.

[pliard1, 2012-11-14 12:34:10]

On 2012/11/13 19:34:44, Mark Mentovai wrote:

LGTM, thanks Mark for fixing this!

Feng asked me to take a look at your change.

[xiaofeng, 2012-11-14 13:24:35]

On 2012/11/13 19:34:44, Mark Mentovai wrote:

LGTM

I'll submit this patch to protobuf trunk. Thanks for contributing the patch.

[Mark Mentovai, 2012-11-14 13:58:12]

Thanks, guys.