pthread_cond_timedwait() is not usable on Darwin, because it cannot be configured to use the monotonic clock. So instead the relative pthread_cond_timedwait_relative_np() is used with a relative time to wait for.
Only tvhthread_renice() is missing, but there seems to be currently no way on Darwin or FreeBSD to implement per-thread prioritization. The #warning is good, but it breaks with the default -Werror compile flag.