Fix compiler warnings

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%40152

src/video/dummy/SDL_nullvideo.c

@@ -42,6 +42,7 @@ static char rcsid =
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
 #include "SDL.h"
 #include "SDL_error.h"