reduce some unneeded warnings.

libc/stdio/_stdio.c

@@ -195,7 +195,6 @@ void _stdio_term(void)
 	 * chain might be corrupt due to a partial store.
 	 */
 	STDIO_INIT_MUTEX(_stdio_openlist_add_lock);
-#warning check
 #ifdef __STDIO_BUFFERS
 	STDIO_INIT_MUTEX(_stdio_openlist_del_lock);
 #endif

libc/stdio/fflush.c

@@ -97,8 +97,6 @@ int fflush_unlocked(register FILE *stream)
 		while(stream) {
 			/* We only care about currently writing streams and do not want to
 			 * block trying to obtain mutexes on non-writing streams. */
-#warning fix for nonatomic
-#warning unnecessary check if no threads
 			if (__STDIO_STREAM_IS_WRITING(stream)) { /* ONLY IF ATOMIC!!! */
 				__MY_STDIO_THREADLOCK(stream);
 				/* Need to check again once we have the lock. */

libc/stdio/popen.c

@@ -124,8 +124,6 @@ FILE *popen(const char *command, const char *modes)
 	return NULL;
 }
 
-#warning is pclose correct wrt the new mutex semantics?
-
 int pclose(FILE *stream)
 {
 	struct popen_list_item *p;