gEDA-user: pcb insulator layer

[DJ Delorie]

> Yes, this looks like the one that's going to get me looking at the
> pcb code again.  Hints on any keywords or routine names I should
> look at about exporting vias by layer will be appreciated.

It's all in draw.c.  The exporters all call through DrawEverything()
via hid_expose_callback at the bottom of that file.

We already do some magic for layers named "outline" in there.