This reverts commit aa20d7b3e8.
Adding these avpriv functions is absolutely overblown: Muxers
can get the desired duration in a few lines themselves.
In particular, using the parse functions from this file
necessitated parsing the extradata (and entailed exporting
the parsing function), although it was only used to know
whether the frames are self-delimiting, but everything of
interest to a muxer does not depend on this at all.
The commit to be reverted also made several structures
part of the ABI, which should be avoided in general.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
