Reverted atomicops_internals_tsan.h to previous version from SVN as I don't have
<sanitizer/tsan_interface_atomic.h> anywhere on my system nor the systems used
by the CI. I have no idea why Google think it should be on a system, except that
the guy submitting the patch at https://code.google.com/p/protobuf/issues/detail?id=607
said so.