[PATCH 0/3] Fix semaphore destruction (BZ #12674)

[Torvald Riegel]

This patch set fixes
https://sourceware.org/bugzilla/show_bug.cgi?id=12674 by either using
64b atomic operations (where available), or by using two separate fields
when only 32b atomic operations are available.  In the latter case, we
keep a conservative estimate of whether there are any waiting threads in
one bit of the field that counts the number of available tokens, thus
allowing sem_post to atomically both add a token and determine whether
it needs to call futex_wake.

The first two patches are changes to the tests, the last big patch is
where the actual fix resides.