Re: Documentation and explanatory diagrams

Excerpts from Rafael Martinez's message of jue jul 01 15:11:31 -0400 2010:

> If we go ahead with having explanatory diagrams, how do you want me to
> send you new/updated diagrams (src&png)? Last time I try to send a large
> attachment to the list, the e-mail was not deliver to the list. Maybe I
> can make them available via an URL.

I think we should have a Makefile rule to build the PNGs from the source
dia files; this seems absent from this patch.  (This means you shouldn't
send PNG files around.)

I'm not sure if this means that we don't want to have the PNG files in
our SCM though, because it'd make the doc unbuildable for those without
access to dia.