Add missing inclusion of libavutil/intreadwrite.h, fix compilation when

libtheora is enabled.

Originally committed as revision 16562 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/libtheoraenc.c

@@ -31,6 +31,7 @@
  */
 
 /* FFmpeg includes */
+#include "libavutil/intreadwrite.h"
 #include "libavutil/log.h"
 #include "avcodec.h"