Fix build: Add intreadwrite.h and bswap.h #includes where necessary.

Originally committed as revision 16556 to svn://svn.ffmpeg.org/ffmpeg/trunk
diff --git a/libavcodec/8bps.c b/libavcodec/8bps.c
index 4376d07..5a5f764 100644
--- a/libavcodec/8bps.c
+++ b/libavcodec/8bps.c
@@ -34,6 +34,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+#include "libavutil/intreadwrite.h"
 #include "avcodec.h"