dvdnav: fix time display when starting in the middle of the DVD

libdvdnav can actually jump into the middle of the DVD (e.g. scene
selection menus do that). Then time display is incorrect: we start from
0, even though playback time is somewhere else. This really matters when
seeking. If the display time mismatches, a small relative seek will
apparently jump to the beginning of the movie.

Fix this by initializing the PTS stuff on opening. We have to do this
after some small amount of data has been read from the stream (because
libdvdnav is crap and doesn't always update the time between seeks and
the first read; also see STREAM_CTRL_GET_CURRENT_TIME remarks in
cache.c; although this was not observed when testing with scene
selection menus). On the other hand, we want to do it before opening the
demuxer, because that will read large amounts of data and likely will
change the stream position.

Also see commit 49813670.
audio: don't wait for draining if paused

Logic for this was missing from pull.c. For push.c it was missing if the
driver didn't support it. But even if the driver supported it (such as
with ao_alsa), strange behavior was observed by users. See issue #933.

Always check explicitly whether the AO is in paused mode, and if so,
don't drain.

Possibly fixes #933.

CC: @mpv-player/stable
audio: drop buffered audio when switching tracks or filters

No reason to wait until the audio has been played. This isn't a problem
with gapless audio disabled, and since gapless is now default, this
behavior might be perceived as regression.

CC: @mpv-player/stable
player: remove some inactive code

demux_seek() actually doesn't return seek success. Instead, it fails if
the demuxer is flagged as unseekable (but this is checked explicitly at
the beginning of this function), or if the seek target PTS is
MP_NOPTS_VALUE (which can never happen).
config: adjust config parser messages

Some cleanup. Also, try not to call mp_msg multiple times for 1 line.
Remove some mp_msg calls with no trailing \n

The final goal is all mp_msg calls produce complete lines. We want this
because otherwise, race conditions could corrupt the terminal output,
and it's inconvenient for the client API too. This commit works towards
this goal. There's still code that has this not fixed yet, though.
command: don't show VO information in colorspace properties

Until now, changing the properties showed the VO colorspace parameters
on OSD. This didn't work quite well, because it showed the VO parameters
_before_ the change. This is because at least one video frame with the
new parameters has to be shown, and this doesn't happen right after
changing the property, but a bit later.

Also fix a random typo in unrelated code.