scePthreadCancel and pthread_cancel threw, scePthreadTestcancel did
nothing and the cleanup handler exports did not exist.
A cancel request is now recorded on the thread and acted on at
scePthreadTestcancel, the condition variable waits, scePthreadSem and
sem waits, scePthreadJoin and the sleeps, and under their POSIX names.
A thread blocked in one of the waits is woken; a condition wait takes
its mutex back before the thread exits. The thread exits with
PTHREAD_CANCELED through scePthreadExit, which now runs the handlers
of __pthread_cleanup_push_imp and __pthread_cleanup_pop_imp.
scePthreadSetcancelstate and scePthreadSetcanceltype reject unknown
values, and pthread_setcanceltype is added.
Constants, the handler node layout and the order of events follow
FreeBSD libthr. A sleep is not interrupted, file and socket calls are
not cancellation points and the asynchronous type acts like the
deferred one except at the two set calls (TechnicalDebt). New test:
guest_pthread_cancel.
