change extradata type to uint8_t *

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@6551 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/avcodec.h

@@ -741,7 +741,7 @@ typedef struct AVCodecContext {
      * - encoding: set/allocated/freed by lavc.
      * - decoding: set/allocated/freed by user.
      */
-    void *extradata;
+    uint8_t *extradata;
     int extradata_size;
 
     /**