[Groff] color support in grodvi

[Werner LEMBERG]

I've added color support in grodvi.

Currently, drawing commands are restricted: the drawing color is always
black, and fill color values are translated to gray.

This restriction is due to the used dvi specials: tpic 2.0 has no
possibility to specify colors except gray shades for filling.

Any idea what I could use instead?  It seems that raw PS is the only
alternative.  Extending the tpic command set would be ideally the best
thing, but all dvi drivers have to be updated which would take a loong
time (maybe this will never happen)...


    Werner