"unary minus operator applied to unsigned type, result still unsigned"

https://codereview.appspot.com/86030044/

Replace TSan API declarations in atomicops_internals_tsan.h with a header inclusion (patch from glider@)

Both gcc and clang defines the __aarch64__ macro when building
for the 64-bit AArch64 execution state of ARMv8 processors, so
use this to detect the architecture.

set.