The implementation of the FUTEX_WAIT option in futex(2) is subtly broken.

The implementation of the FUTEX_WAIT option in futex(2) is subtly broken.
Unfortunately libc and libpthread rely on the broken behaviour.  Adjust
the code in those libraries such that it works with both the old and the
proposed new behaviour.  The kernel changes that fix the issue will be
committed in a week or so to give those who do their own builds a chance
to update these libraries before we make the change.

ok mpi@, deraadt@