Add missing stdint.h #include to headers that use it.

Originally committed as revision 12429 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/intfloat_readwrite.h

@@ -21,6 +21,7 @@
 #ifndef FFMPEG_INTFLOAT_READWRITE_H
 #define FFMPEG_INTFLOAT_READWRITE_H
 
+#include <stdint.h>
 #include "common.h"
 
 /* IEEE 80 bits extended float */

libavutil/mathematics.h

@@ -21,6 +21,7 @@
 #ifndef FFMPEG_MATHEMATICS_H
 #define FFMPEG_MATHEMATICS_H
 
+#include <stdint.h>
 #include "rational.h"
 
 enum AVRounding {