gEDA-dev: Diode symbols in GSchem and PCB

[DJ Delorie]

> That's why I think the best/easiest way to modify gEDA is to enable
> promotion of pin attribues into the .sch file so they may be edited
> directly on the schematic using gschem or bulk edited in a
> spreadsheet using gattrib.

We also talked about an "attribute helper hook" that could query some
external program to obtain more attributes.  Perhaps pin numbers and
slotting could be part of that plan, assuming we persue it?