arxana update

I finished a better version of the "hierarchical browser", so now it
is possible to scroll DOWN through the hierarchy of a latex document.
(Moving up or sideways or whatever will not be hard to code up,
indeed, I can probably just reuse a lot of the code I already wrote
for my last prototype!)

I used a lot of higher-order functions to make things flexible -- the
basic "browser" is just a list of items, but when you "click" on them,
they do different things. For example, if you click on an article, it
displays the article, whereas if you click on a section, it displays a
new list of that section's contents. (So, a lot like Gopher or
dired.)

Higher-order functions can be built and then called to do formatting
"to order". I admit it takes a little getting used to! If you want
to see how gnarly things can get, take a look in the vicinity of Note
5.35 (page 18) in

http://planetx.cc.vt.edu/~jcorneli/arxana/arxana.dvi

Presumably the code can eventually be simplified somewhat, but anyway,
other than making my head spin a bit, I'm happy to note that I haven't
run into any critical difficulties in the course of assembling what
should be considered a "basic functionality".

(It would be swell to run some traces or whatever other benchmarking
things exist to make sure I'm not secretly making the machine work too
hard -- but I don't think I am!)

Other than finishing the "nice" features of Hierarchies (which I might
table for a bit now that I've got the core done), I've got a few
interesting things related to the lisp-to-database connection to
figure out, but other than that it looks like a handful of relatively
trivial things to do before I have something together that I think is
release-worthy.