Fix compilation with --enable-libxvid.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@16655 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/libxvidff.c

@@ -28,6 +28,7 @@
 #include <xvid.h>
 #include <unistd.h>
 #include "avcodec.h"
+#include "libavutil/intreadwrite.h"
 #include "libxvid_internal.h"
 
 /**