options: change --volstep to 2

With default settings, this allows you to hit the 100% mark (with
default --softvol-max in the middle) even if you've reached min or max
volume before. This is because 50 is not divisible by 3 (old default)
but by 2 (new default).

Not really sure why there still can be issues with higher --softvol-max
and --volstep=1, but this is where I stop caring.
video: wake up core as soon as possible

There's no reason to let the core wait until the frame is done
displaying. In practice, the core normally didn't need this additional
wakeup, and the VO was quick enough to fetch the new frame, before the
core even attempted to queue a new frame. But it wasn't entirely clean,
and the correct wakeup handling might matter in some cases.
TOOLS/mpv_identify.sh: simplify line-by-line reading

Use here-document idiom to read mpv output line-by-line.
TOOLS: eliminate echoes with variable substitutions

echo behaviour with backslash escapes seems to be non-portable: dash does
expand such an escapes and bash does not, so use cat/printf instead.
ao_oss: move code around

More logical, and preparation for the next commit. No functional
changes.
ao_oss: prevent hang when unpausing after device was lost

Pausing/unpausing while the audio device can't be reopened, and then
unpausing again when the device is finally reopened, can hang the
player for a while.

This happens because p->prepause_samples grows without bounds each
time the player is unpaused while the device is lost. On unpause,
ao_oss plays prepause_samples of silence to compensate for A/V timing
issues due to the partially lost buffer (we can't pause the device at
an arbitrary sample position, and the current period will be lost).
This in turn will make the player appear to be frozen if too much
audio is queued. (Normally, play() must never block, but here it
happens because more data is written than get_space() reports. A
better implementation would never let prepause_samples grow larger
than the period size.)

The unbounded growth happens because get_space() always returns that
the device can be written while the device is lost. So limit it to
200ms. (A better implementation would limit it to the period size.)

Also see #1080.
TOOLS/idet.sh: Handle the case of multiple Parsed_idet_0: output lines.

This seems to happen frequently now. It is handled by adding their values.