AAlib driver was using C runtime string functions without including string.h.

  Fixes Bugzilla #131.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%401323

src/video/aalib/SDL_aavideo.c

@@ -25,6 +25,7 @@
 
 #include <stdlib.h>
 #include <stdio.h>
+#include <string.h>
 #include <unistd.h>
 #include <sys/stat.h>