gEDA-dev: PCB Library regression

[DJ Delorie]

> I hope to see at some point, a pluggable interface for footprint
> listing,

We already have one.  pcb can run *any* command to query the footprint
library and extract a footprint from it.  The "m4" library is that,
with m4 as the program.

> I'll admit to not having tried it, but _why_ can't m4 be run on windows.
> A brief google search suggests that GNU M4 can compile natively with
> windows, and that people have produced a native m4.exe in the past.

It's not that it can't, it's that it isn't there by default.  Plus,
we'd been having problems with "special" characters in m4 footprint
names, so the less dependency on m4 we have, the better.