A better fix for building DGA code on Solaris 8, inspired by the NetBSD pkgsrc patch.

--HG--
branch : SDL-1.2
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/branches/SDL-1.2%402506

src/video/dga/SDL_dgavideo.h

@@ -25,6 +25,7 @@
 #define _SDL_dgavideo_h
 
 #include <X11/Xlib.h>
+#include <X11/Xlibint.h>
 #include <X11/Xproto.h>
 
 #include "SDL_mouse.h"