linuxthreads.old: fix typo in pthread_mutex_unlock hidden prototype

Reported-by: Tony Wu <tung7970@gmail.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

libpthread/linuxthreads.old/internals.h

@@ -511,7 +511,7 @@ extern __typeof(pthread_mutex_init) __pthread_mutex_init attribute_hidden;
 extern __typeof(pthread_mutex_destroy) __pthread_mutex_destroy attribute_hidden;
 extern __typeof(pthread_mutex_lock) __pthread_mutex_lock attribute_hidden;
 extern __typeof(pthread_mutex_trylock) __pthread_mutex_trylock attribute_hidden;
-extern __typeof(pthread_mutex_unlock) __pthread_mutex_attribute_hidden;
+extern __typeof(pthread_mutex_unlock) __pthread_mutex_unlock attribute_hidden;
 #endif
 
 /* Prototypes for some of the new semaphore functions.  */