cid 1191737

- Previous algorithm was unable to guess the first packet
pts because of ogg design (some codecs/opus/vorbis have total
sample at page granule and only granule on last packet. You
then need to compute first packet pts backward using packets
duration).
So we were stuck either assuming a start at pts/pcr zero, or
be unable to handle ogg streaming (non zero start) correctly,
or had to always drop the 0..N-1 packets for first page.
We need libvorbis to correcly compute those durations (code
is far more complex than opus's one).
- Refactorized to discard the tons of cases appended
with each new codec.
- lots of other fixes in many places

Because event will rebuild chapter variable.

because make_path strips last segment

Two different buttons signify to the user that there is an
actual difference in using either of these. But in fact,
both call the same code and if the folder is misnamed, even
the BDMV button would classify the folder as a DVD type.

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Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>