Cleanup new cxa guard implementation.

* Add TSAN annotations around the futex syscalls.
* Test that the futex syscall wrappers actually work.
* Fix bad names.

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@359069 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 11fe87d836527d01c0df6f8ad25d575c9baba7cc)

Bug: http://b/189279320
Test: treehugger
Change-Id: I73ce984b425d40addd9b951370ec7d36fccfe010
3 files changed