Doxygen - another sample, preliminary comments

[Benjamin Kosnik]

All this Doxygen stuff looks extremely promising. I'd like to start
checking in patches to make the libstdc++ documentation use it.

>From where I'm sitting, this is what I'd like to see:

1) minimal changes to the source files 
(I will, however, accept changes to the source files to get these
docs. The changes appear to be quite minimal)

2) some kind of script for getting consistent, up-to-date output with
   the minimum of manual tweaking. The more we can automate this with
   scripts, the better. After we get a script that's working, we can
   just add a Makefile rule, similar to the old TAGS rule.

sound sane?

Perhaps this stuff should begin after the 2.91 release though. Phil,
what's the status of the documentation WRT this release? Should we
just go with what we've got?

-benjamin