[tex4ht] dependencies, new and incomplete

[Michal Hoftich]

Hi Karl,

I've just added basic support for skak package, so I could test
whether the html4.4ht contains configurations for skak.4ht. It doesn't
:


>
> 2) Nevertheless, by grepping the logs, I see that nearly everything
> depends on mktex4ht.4ht and tex4ht.sty. I just added those as common
> dependencies (except for the files which generate them). Hope it helps
> and doesn't break anything. Easy enough to revert/tweak, of course.

I  think that this change causes massive recompilations even after
minor changes. I think better solution could be to compile the seeding
files (tex4ht-html4.tex and so on) twice when they were changed.

Best regards,
Michal