to PTHREAD_MUTEX_NORMAL.
(pthread_mutex::unlock): Return EPERM if the mutex has no owner and
the mutex type is PTHREAD_MUTEX_ERRORCHECK, as on Linux.
(pthread_mutexattr::pthread_mutexattr): Ditto.
(pthread_mutex_unlock): Do not fail if mutex is a normal mutex
initializer.
* include/pthread.h (PTHREAD_MUTEX_INITIALIZER): Redefine as
PTHREAD_NORMAL_MUTEX_INITIALIZER_NP.