options: add mechanism to add sub-options from component lists

There are a lot of ad-hoc component lists in mpv: for example the stream
and demuxer lists. It doesn't seem to make sense to add any abstractions
around it since they are completely trivial and have very specific
probing mechanisms and so on, so they will remain ad-hoc.

This commits add a way to let these add arbitrary per-component options,
without giving up the ad-hoc way, and without having to dump them into
options.c with lots of ifdeffery (like it was done until now).

Also see next commit.

0 files changed, 0 insertions, 0 deletions