Log Message:
Import iverilog (Icarus Verilog) 10.1.1 as cad/iverilog

It's a rename of cad/verilog to a better name.

Updated DESCR for new package:

Icarus Verilog is intended to compile ALL of the Verilog HDL as described in
the IEEE-1364 standard. Of course, it's not quite there yet. It does currently
handle a mix of structural and behavioral constructs.

Icarus Verilog is not aimed at being a simulator in the traditional sense, but
a compiler that generates code employed by back-end tools.

No objections to rename from <gdt>