Do not reallocate AVPacket's data when muxing a packet

Originally committed as revision 16616 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/avc.h

@@ -25,7 +25,7 @@
 #include <stdint.h>
 #include "avio.h"
 
-int ff_avc_parse_nal_units(const uint8_t *buf_in, uint8_t **buf, int *size);
+void ff_avc_parse_nal_units(ByteIOContext *s, const uint8_t *buf, int size);
 int ff_isom_write_avcc(ByteIOContext *pb, const uint8_t *data, int len);
 const uint8_t *ff_avc_find_startcode(const uint8_t *p, const uint8_t *end);