Build issue with latest FFMpeg

[andreili]

Have a issue on OS with a latest FFMpeg, installed on it:

util/ffmpeg/remuxer.c: In function 'ffmpeg_remuxer_init_avcontext':
util/ffmpeg/remuxer.c:23:115: error: passing argument 6 of 'avio_alloc_context' from incompatible pointer type [-Wincompatible-pointer-types]
   23 |   avio = avio_alloc_context(buffer, buffer_size, output, remuxer->opaque, output ? NULL : packet, output ? packet : NULL, NULL);
      |                                                                                                                   ^
      |                                                                                                                   |
      |                                                                                                                   int (*)(void *, uint8_t *, int) {aka int (*)(void *, unsigned char *, int)}
In file included from util/ffmpeg/remuxer.h:5,
                 from util/ffmpeg/remuxer.c:1:
/usr/include/libavformat/avio.h:404:25: note: expected 'int (*)(void *, const uint8_t *, int)' {aka 'int (*)(void *, const unsigned char *, int)'} but argument is of type 'int (*)(void *, uint8_t *, int)' {aka 'int (*)(void *, unsigned char *, int)'}
  404 |                   int (*write_packet)(void *opaque, const uint8_t *buf, int buf_size),
      |                   ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
make[1]: *** [Makefile:103: util/ffmpeg/remuxer.o] Error 1

This changes are merged on FFMpeg library a year ago and need to use a new function prototype: FFmpeg/FFmpeg@02aea61