Dotted and dashed ellipses.

In troff mode, dotted and dashed splines.

Make DELIMITED have type lstr; this would allow us to give better
error messages for problems within the body of for and if constructs.

In troff mode without -x, fake \D't' with .ps commands.

Perhaps an option to set command char.

Add an output class for dumb line printers. It wouldn't be pretty
but it would be better than nothing. Integrate it with texinfo.

Option to allow better positioning of arrowheads on arcs.

Perhaps add PostScript output mode.

Change the interface to the output class so that output devices have
the opportunity to handle arrowheads themselves.

Consider whether the line thickness should scale.

Consider whether the tesg in a for loop should be fuzzy (as it is in grap).

Possibly change fillval so that zero is black.
