[v3] initial Doxygen doc-generation support added

[Rich Churcher]

> There are a lot of good ideas and suggestions that have been bouncing
> around the v3 list regarding doxygen; I figured if I actually updated
> that placeholder script with something useful, more people could 
> chime in.

Hi Phil.  As you may recall, I did a couple of test runs with Doxygen
last year and was never heard from again :o)  To be honest, I was a bit
stumped as to what direction to take with the documentation given the
discussion on maintainer vs. user documentation.  I'd like to ask that
we define a bit more clearly what we're looking for in the way of user
information, as I would still like to help with this.

Put another way, what do you see as "important, but lacking" in this
area?

Cheers,
Rich.