gEDA-user: [pcb] flexible max layers patch is IN!

[DJ Delorie <dj@xxxxxxxxxxx>]

Ok folks, this is a fun one.  I just checked in a set of patches from
me and Bill that teach PCB how to change the number of layers in a
board.  The default is still 8, but the default maximum is now set to
16 (easily changed via recompile), and you can add, delete, and move
layers.

So you can create a two layer board that actually has just two layers!
Or you can add more copper or "special" layers (pcb doesn't treat them
any different than before, there's just more of them).  Eight layer
board with an outline is now possible by default, for example.  And
you can add internal layers and rearrange them to reflect your
stacking order.

Also, unlike changing layers in the past, PCB will detect the number
of layers in your *.pcb files when they're loaded, so you don't need
multiple copies of the pcb binaries to support multiple board sizes.

Note that the *.pcb file format hasn't changed; new PCBs can load old
files just fine.  Old PCBs can load new files as long as they have
exactly eight layers.

Caveat: don't delete a layer with stuff on it.  It won't warn and
can't undo all that yet.  There's probably some memory leaks in
deleting layers too, so if you spend all day deleting layers you might
run out of memory ;-)

Let us know if you find any bugs.