audio/out: remove old things

Remove the unnecessary indirection through ao fields.

Also fix the inverted result of AOCONTROL_HAS_TEMP_VOLUME. Hopefully the
change is equivalent. But actually, it looks like the old code did it
wrong.
mplayer-input.conf: fix broken binding

"#" starts a comment, so the # key needs to be handled specially.
MPlayer has the same issue, but its input.conf is wrong. Or at least I
think it's wrong; looking at the MPlayer code it's doubtful they somehow
special-case and handle this.
ao_oss: minor simplification

Equivalent code.
ao_pcm: minor simplification
ao_sndio: fix a comment

Whether this code was written with the correct assumptions in mind, I
don't know.
audio/out: always round get_space on period size

Round get_space() results in the same way play() rounds the input size.
Some audio APIs do this for various reasons.

This affects only "push" based AOs. Some of these need no change,
because they either do it already right (like ao_openal), or they seem
not to have any such requirements (like ao_pulse).

Needed for the following commit.
audio/out/push: redo audio waiting

Improve the logic how the audio thread decides how to wait until the AO
is ready for new data. The previous commit makes some of this easier,
although it turned out that it wasn't required, and we still can handle
AOs with bad get_space implementation (although the new code prints an
error message, and it might fail in obscure situations).

The new code is pretty similar to the old one, and the main thing that
changes is that complicated conditions are tweaked. AO waiting is now
used better (mainly instead of max>0, r>0 is used). Whether to wakeup
is reevaluated every time, instead of somehow doing the wrong thing
and compensating for it with a flag.

This fixes the specific situation when the device buffer is full, and
we don't want to buffer more data. In the old code, this wasn't handled
correctly: the AO went to sleep forever, because it prevented proper
wakeup by the AO driver, and as consequence never asked the core for new
data. Commit 4fa3ffeb was a hack-fix against this, and now that we have
a proper solution, this hack is removed as well.

Also make the refill threshold consistent and always use 1/4 of the
buffer. (The threshold is used for situations when an AO doesn't
support proper waiting or chunked processing.)

This commit will probably cause a bunch of regressions again.
audio: fix initial sync with huge AO buffer

With e.g --start=-3 --audio-buffer=10 the decoder entered EOF state
before the initial sync was finished, entered STATUS_EOF, and just
started playing audio from a random position.

This doesn't handle seeking outside of the file, which is a different
case. E.g. --start=30:00 with audio and video enabled in a file shorter
than 30:00 will play a random last part of audio. This could perhaps be
fixed by using the hr-seek target for cutting audio, instead of the
video PTS, but that would be kind of intrusive, so don't do it for now.
The simpler solution, assuming audio EOF on video EOF, wouldn't work,
because we allow audio to start before video, or to last after video.
stream_lavf: assume icy title data is terminated with ';'

Should fix #1071.