missing include noticed by g0th

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@4582 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/opt.c

@@ -24,6 +24,7 @@
  * @author Michael Niedermayer <michaelni@gmx.at>
  */
  
+#include <stdio.h> //for FILE *
 #include "avcodec.h"
  
 static double av_parse_num(const char *name, char **tail){