TODO

- Improve appearance of the builtin fonts
- Add pattern fill commands 
- [full] color support may be buggy in some modes, and is not implemented
  in the Sun, OS/2 and MS Windows modules
- to_vga, to_atari and to_sunvw do not yet support more than eight colors
  (contributions from MS DOS/Windows, OS/2, Atari and Sun users needed).
- Allow redefinition of PenColor in raster graphics modes
- Optionally use an output formats' text commands where available, instead 
  of converting LB characters to line drawings
- Optionally use an output formats' polygon commands
- Optionally collect all plots from a multi-file or multi-plot run in a 
  single output file if the format allows this (particulary PDF)
- Add miter support in the raster modes, now that we have true wide line
  support