Adds support for the custom ASF container used by some Argonaut Games'
games, such as 'Croc! Legend of the Gobbos', and 'Croc 2'.

Can also handle the sample files in:
https://samples.ffmpeg.org/game-formats/brender/part2.zipSigned-off-by: Zane van Iperen <zane@zanevaniperen.com>