* thread.h (pthread::cleanup_stack): Renamed cleanup_handlers to
cleanup_stack.
* thread.cc (pthread::pthread): Ditto.
(pthread::create): Fixed mutex verification.
(pthread::push_cleanup_handler): Renamed cleanup_handlers to
cleanup_stack.
Mutex calls removed, used InterlockedExchangePointer instead.
(pthread::pop_cleanup_handler): Renamed cleanup_handlers to
cleanup_stack.
(pthread::pop_all_cleanup_handlers): Ditto.
(__pthread_once): Check state first and return if already done.
(__pthread_join): DEADLOCK test reverted to __pthread_equal
call.
(__pthread_detach): Unlock mutex before deletion.