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