pthread_cond_broadcast had no test, and no test checked that one broadcast
wakes every waiter. Check the FreeBSD 11.4 results of _pthread_cond_broadcast
(lib/libthr/thread/thr_cond.c lines 495-544): a broadcast without waiters
returns 0, a statically initialised condition variable is initialised and
returns 0, a destroyed one returns EINVAL (22), and one broadcast wakes all
three waiting threads.
Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
