* Use the longer name ThreadSanitizer rather than TSan for the new files.
* Don't implement `tsan::consume` at all for now.
* Do the `tsan::release` for `ulock_unlock()` at the head of the function,
not at the tail.
* Add a comment to test/Sanitizers/tsan/once.swift to explain the test a
little more clearly.
rdar://110665213
