lavf: const correctness for avformat_new_stream

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavformat/avformat.h

@@ -1311,7 +1311,7 @@ const AVClass *avformat_get_class(void);
  *
  * @return newly created stream or NULL on error.
  */
-AVStream *avformat_new_stream(AVFormatContext *s, AVCodec *c);
+AVStream *avformat_new_stream(AVFormatContext *s, const AVCodec *c);
 
 AVProgram *av_new_program(AVFormatContext *s, int id);
 

libavformat/utils.c

@@ -3101,7 +3101,7 @@ AVStream *av_new_stream(AVFormatContext *s, int id)
 }
 #endif
 
-AVStream *avformat_new_stream(AVFormatContext *s, AVCodec *c)
+AVStream *avformat_new_stream(AVFormatContext *s, const AVCodec *c)
 {
     AVStream *st;
     int i;