include intreadwrite.h, fix compilation, img2.c use AV_RL32

Originally committed as revision 16595 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/img2.c

@@ -20,6 +20,7 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#include "libavutil/intreadwrite.h"
 #include "libavutil/avstring.h"
 #include "avformat.h"
 #include <strings.h>