gEDA: FNF: Netlist format for Confluence and Informal

[Tom Hawkins <tom-at-NOSPAMconfluent_dot_org>]

I started to define the format for FNF: the future netlist format of 
Confluence and InFormal.

FNF is a flat netlist that retains hierarchical scoping.  The netlist is 
a directed graph of primitive RTL operations, called cells. Some basics:
   - All cells have 0 or 1 outputs.
   - All cells operate on bit vectors.

The syntax definition is located here:

   http://www.confluent.org/wiki/doku.php?id=fnf:main

(Steve, hopefully this aligns with Icarus synthesis, when you move it 
from bits to vectors.)

Shortly I will release an FNF generator for Icarus, followed by a 
Verilog, VHDL, C, and NuSMV writer.

Confluence Users, this should enable the following at some point in the 
future:
   - Hierarchical HDL.
   - 4-state C simulation models (01XZ), with VCD on all internals.
   - Back annotation.

All comments are welcome.

-Tom