fails:C-API Mutex functions rb_mutex_new creates a new mutex
fails:C-API Mutex functions rb_mutex_locked_p returns true if the mutex is locked
fails:C-API Mutex functions rb_mutex_trylock locks the mutex if not locked
fails:C-API Mutex functions rb_mutex_trylock returns false if the mutex is already locked
fails:C-API Mutex functions rb_mutex_lock returns when the mutex isn't locked
fails:C-API Mutex functions rb_mutex_lock throws an exception when already locked in the same thread
fails:C-API Mutex functions rb_mutex_unlock raises an exception when not locked
fails:C-API Mutex functions rb_mutex_unlock unlocks the mutex when locked
fails:C-API Mutex functions rb_mutex_sleep throws an exception when the mutex is not locked
fails:C-API Mutex functions rb_mutex_sleep sleeps when the mutex is locked
fails:C-API Mutex functions rb_mutex_synchronize calls the function while the mutex is locked
