[tex-k] dvitomp update: support \Black, \Red, and similar colordvi commands

[Eddie Kohler]

> The reason why I never implemented dvi specials in dvitomp was mostly
> laziness, but I also thought that there wasn't much of a need.
> 
> A. I wanted to keep the typesetting capabilities as simple as possible and
>    rely on the main part of the MetaPost language for features such as color.
>    I should think that most users could just do something like this:
>      color Cerulean; Cerulean= (0.0600122, 0.889988, 1.0);
>      draw btex This is blue! etex withcolor Cerulean;
>      label(image(draw btex This is blue! etex withcolor Cerulean), z0);

Then you can't easily highlight parts of an equation, etc.

The dvips 'color' specials are standardized and used by the default LaTeX color 
package.  There's a huge set of additional specials, of course, but we should 
worry about those as they came up.

I'm indifferent about dvitomp.web vs. dvitomp.ch.  Both Olaf's and my version 
use convenient functions such as "xstrdup" not available in Pascal/Web, however, 
and it doesn't seem worth it to recode it all in Pascal.

But I wish I had known "image" existed, it would have simplified my life 
considerably. :(

Eddie