This is relatively hacky, but it's Christmas, so it's ok. This does two
things: 1. allow selecting two subtitle tracks, and 2. include a hack
that renders the second subtitle always as toptitle. See manpage
additions how to use this.
For some reason, this checked whether there are external tracks at all
before doing any seeks. Possibly this was to avoid multiple
get_main_demux_pts() calls, but calling this multiple times shouldn't be
too bad.
Since m_option.h and options.h are extremely often included, a lot of
files have to be changed.
Moving path.c/h to options/ is a bit questionable, but since this is
mainly about access to config files (which are also handled in
options/), it's probably ok.
