Use C++11 atomics opportunistically.

Also, fix the barriers for PPC and tidy up in general.

Change-Id: I14a25ac4ca6b0c2e6bba11fb79b69ee730e63512
Reviewed-on: https://code-review.googlesource.com/3707
Reviewed-by: Paul Wankadia <junyer@google.com>
1 file changed