TOOLS: idet: remove unused code
TOOLS, version.sh: shellcheck: replace `cmd` with $(cmd)

Signed-off-by: wm4 <wm4@nowhere>
TOOLS: shellcheck: remove '$' on variables in $(()) expansion
TOOLS: shellcheck: quote variable expansions
TOOLS: idet: use quotes for the verdict value

ShellCheck warns about "vara-varb" about not being in $(()), but we
actually want the literal string, so quote it. Also fix a typo.
command: avoid a double -> int cast

Just check against zero directly.

Changes behavior, but that should be ok.

Signed-off-by: wm4 <wm4@nowhere>
options.lua: call msg.debug after resolving 'identifier'
TOOLS/mpv_identify.sh: mark as executable
demux: gracefully handle packet allocation failures

Now the packet allocation functions can fail.
player: don't let multiline filenames set options on resume

If --write-filename-in-watch-later-config is used, and the filename
contains newline characters (as generally allowed on Unix), then the
newline will be written to the resume file literally, and the parts
after the newline character are interpreted as options.

This is possibly security relevant.

Change newline characters (and in fact any other special characters)
to '_'.

Reported as #1099 (this commit is a reimplementation of the proposed
pull request).

CC: @mpv-player/stable
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.