[Groff] plan9 troff

[Bernd Warken]

The troff of plan 9 is quite interesting, e.g. they draw splines and
functions and they have full wchar Unicode support.

If someone is interesting in the code you can get it with the following
steps.

- http://plan9.bell-labs.com
- register with your name and email address.
- fill in the floppy setup screen (or just do a `continue').
- download the plan9.9gz (large ~60 MB), the comple install incl. source
- `gunzip plan9.9gz' produces a ~150 MB plain text archive.
- in `less' search for the files starting with `/sys/src/cmd/troff'.

Bernd Warken