For pshared semaphore, this commit still does not enable cancellation
point, I think there should be a pthread_enter_cancellation_point_np
for libc to implement a safe cancellation point.
Only warnings that could be fixed without changing the generated object
code and without restructuring the source code have been handled.
Reviewed by: /sbin/md5
so that multiple opens of the same semaphore without an intervening
sem_close() return the same object, and so that sem_close() does not
segfault while trying to remove the item from the list.
