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().

src/mutex.c

@@ -81,18 +81,6 @@ malloc_mutex_init(malloc_mutex_t *mutex)
 	return (false);
 }
 
-void
-malloc_mutex_destroy(malloc_mutex_t *mutex)
-{
-
-#ifndef JEMALLOC_OSSPIN
-	if (pthread_mutex_destroy(mutex) != 0) {
-		malloc_write("<jemalloc>: Error in pthread_mutex_destroy()\n");
-		abort();
-	}
-#endif
-}
-
 void
 malloc_mutex_prefork(malloc_mutex_t *mutex)
 {