input: remove pausing command prefixes

These are now equivalent to combining commands with the "cycle pause" or
"set pause" commands, and thus are not needed anymore. They were also
obscure and undocumented.
manpage: minor corrections
demux_playlist: fix m3u detection logic

Caused failure to detect .pls files, because they were misdetected as
m3u. The problem is that "forcing playlist files" and "forcing a
specific playlist format" are not really treated separate, and in both
cases p->force is set to true. This made m3u detect all files as m3u
if --playlist was used. So correctly check whether the file format is
actually being probed or not.
build: removed undefined behavior from PVR check

This shouldn't matter, but it's probably better if the code to check is
valid - otherwise an extremely clever compiler might fail to compile it,
and the feature would be misdetected. (Probably.)

Found by cppcheck.
player: don't assign "false" to pointer

This is legal in theory. "false" expand to 0, and 0 is a valid pointer
value. But I guess this was not really intended.

Found by cppcheck.
wayland: fix unchecked malloc usage

Found by cppcheck.

Actually untested. (This is the file drag&drop code, I don't even know
which wayland clients support this.)
audio/out: more debugging info for --dump-stats
mixer: make code more readable

You wouldn't have guessed that the bottom-most "level[i] = 0.f;" line
was actually required. It even confused cppcheck.
manpage: update --playlist entry
TOOLS/stats-conv: draw playloop and AO thread events separately

Use for all AO thread events y=0.5, while playloop events remain at y=1.
This makes the graph easier to read.
TOOLS/stats-conv: don't crash on empty lines
audio/out: avoid wakeup feedback loop

When the audio buffer went low, but could not be refilled yet, it could
happen that the AO playback thread and the decode thread could enter a
wakeup feedback loop, causing up to 100% CPU usage doing nothing. This
happened because the decoder thread would wake up the AO thread when
writing 0 bytes of newly decoded data, and the AO thread in reaction
wakes up the decoder thread after writing 0 bytes to the AO buffer.

Fix this by waking up the decoder thread only if data was actually
played or queued. (This will still cause some redundant wakeups, but
will eventually settle down, reducing CPU usage close to ideal.)
audio/out: fix previous commit

This didn't quite work. The main issue was that get_space tries to be
clever to reduce overall buffering, so it will cause the playloop to
decode and queue only as much audio as is needed to refill the AO in
reasonable time. Also, even if ignoring the problem, the logic of the
previous commit was slightly broken. (This required a few retries,
because I couldn't reproduce the issue on my own machine.)
vd_lavc: Support hwaccel 1.2 and later

Hwaccel 1.2 populates only the third data field and assumes
that the AVCodecContext is available to the dealloc function.
vda: Simplify codec selection

VDA supports h264 only.
vda: Hwaccel 1.2 support

Use the new context and the default functions provided.
build: fix OpenBSD DVD/CDROM device names

Closes #781.
player: disable hr-seek framedropping during backstepping
stream_smb: increase to 128k read_chuuk from default 8k

Previous to this commit, read_chunk was not set in stream_smb. The
cache was therefore filled in small 8K chunks. This resulted in poor
performance when compared to, for example, smbnetfs on the same
network.

The value of 128k is chosen both because it is emperically
the "levelling off point" for throughput into mpv's cache, and because
it is the value chosen by smbnetfs when serving smb shares to
mpv.

Note that this change has no effect unless --cache is explicitly
specified as smb:// streams do not activate cache by default. This is
because the default cache size of 320K is so small it actually makes
smb:// perfomance worse. For best results use at least --cache=1024.
old-build: define a new symbol

waf has a proper test, but no test was added to old-configure.

This means that on OSX, old-configure is not supposed to work anymore.
But still allow it to compile cleanly on OSX.