Add the ability to rename nets

[ahvezda]

> I want VSS be the same as GND. I made a piece of
> net in gschem, connected it to the ground, named
> VSS and nothing happened. Then I removed this and
> renamed some other existing net that connected
> some capacitor to GND with name VSS and it
> works however:

>1) why it works for one piece of net and not another?
>2) I get this warning message from gsch2pcb:
>
> Found duplicate net name, renaming [GND] to [VSS]
> WARNING: Trying to rename something twice:
> GND and GND
>are both a src and dest name
>
>This warning is okay if you have multiple levels
>of hierarchy!
>3) The resulting net in the *.net file is called
>VSS and I like GND more.

A temporary work around to this is to create a symbol
which contains:

v 20040111 1
P 100 100 300 100 1 0 1
{
T 100 300 5 6 0 0 0 0 1
pinnumber=1
T 100 200 5 6 0 0 0 0 1
pinseq=1
}
L 0 200 100 100 3 0 0 0 -1 -1
L 100 100 0 0 3 0 0 0 -1 -1
T 100 400 8 10 0 0 0 0 1
device=none
T 100 600 8 6 0 0 0 0 1
net=rename:1

and attach it to the free floating net. You also have
to have:

(net-naming-priority "netname")

set in a gnetlistrc file for this to work. This is not
an ideal fix since it breaks other things.