[MPlayer-dev-eng] NUT cleanup

[Rich Felker]

Somehow I missed the biggest deprecated-looking thing I found in the
draft! I dunno how I could forget it..

In stream_header, the average_bitrate field. There's no way this can
be known at the time it's written, and it's not useful to the player
IMO. If you want to store a "nominal" bitrate (or an actual bitrate
after a second pass of remuxing), it could be stored in an info tag,
but I don't see how something so useless and arbitrary belongs in the
stream header.

If it's necessary in order for some broken proprietary codecs to work,
it should be in their codec-private extradata. IMO the only such
codecs are legacy windows binary codecs, if any at all, and they
probably need full bitmapinfoheader crap or whatever already anyway..

Rich