add mutex_unlock_and_sleep()
add test for mutex_unlock_and_sleep()
Fix `pthread_mutex_lock()` check in test_pthread_cooperation
Merge pull request #728 from BytesGalore/add_unlock_mutex_and_sleep

core:mutex: enable atomic execution of unlock a mutex and sleep for a thread
Merge pull request #849 from Kijewski/issue-844

posix: Fix `pthread_mutex_lock()` check in test_pthread_cooperation