So I don't have to keep duplicating file names all over the place, I've
decided to use the "dox" extension on text files that are formatted for
doxygen processing. This way, doxygen can search for them using wildcards,
and unformated text files won't cause any headaches.
Use subpage instead of ref. This actually moves the so-referenced pages out
of "Related Pages". I imagine they'll form a tree in the menu, but I don't have
that config here.