Docs for debugging enhancements

[Neil Jerram]

I've put the docs for some debugging enhancements that I've been
working on up at
http://www.ossau.uklinux.net/guile-debugging/index.html, and would be
most interested in any comments.

(This is a revamp of earlier work in a package called
guile-debugger-0.7 and in Guile CVS, but now quite a lot different and
IMO better.)

(I'm travelling at the moment, hence (i) sending from Outlook and (ii)
why I can't yet release the whole package.  But I will do (ii) in the
next week or so.)

Regards,
    Neil