Remove ephemeral mutexes.

Remove ephemeral mutexes from the prof machinery, and remove
malloc_mutex_destroy().  This simplifies mutex management on systems
that call malloc()/free() inside pthread_mutex_{create,destroy}().

Add atomic_*_u() for operation on unsigned values.

Fix prof_printf() to call malloc_vsnprintf() rather than
malloc_snprintf().

include/jemalloc/internal/mutex.h

@@ -28,7 +28,6 @@ extern bool isthreaded;
 #endif
 
 bool	malloc_mutex_init(malloc_mutex_t *mutex);
-void	malloc_mutex_destroy(malloc_mutex_t *mutex);
 void	malloc_mutex_prefork(malloc_mutex_t *mutex);
 void	malloc_mutex_postfork_parent(malloc_mutex_t *mutex);
 void	malloc_mutex_postfork_child(malloc_mutex_t *mutex);