[help-texinfo] proof-of-concept documentation category system

Hi Robert,

    Here is some example output. The list of categories is near the end of
    this page.
    http://maxima.sourceforge.net/misc/tmp-categories-html/tmp-target_toc.html

I'm afraid I don't understand.  Your example here seems to be within a
single manual.  In that case, can't you just use an index for this
purpose?  (Whether or not it's called an "index" in the output.)

Oh, I guess you want to have the categories included in the actual
output, too, e.g.,
http://maxima.sourceforge.net/misc/tmp-categories-html/tmp-target_36.html#genindex
That can't be done with an index, although adding a feature to indexes
to make it possible seems fairly feasible.  I'm not sure, but I don't
think hardwiring knowledge of "Categories" as a special case is the best
general approach.

    http://en.wikipedia.org/wiki/Jim_Jarmusch

The interesting thing about the wikipedia categories is that they cut
across articles, of course.

The equivalent feature in Texinfo is @dircategory, although it is
definitely underdeveloped and underused.  In particular, forcing the dir
file to be a single node is highly problematic if there were going to be
thousands of Texinfo categories.  It's already problematic to list every
libc function, which is, after all, part of the idea of Info (replace
man).  However, changing this is unfortunately not easy.

Best,
Karl