Additions to simulation support.

Adds verilator support: systemC and C++ descritions.
Convert verilog define files (.v) into C define files (.h).
Adds icarus specific dependencies.

	modified:   orpsoc/core.py
	modified:   orpsoc/simulator/icarus.py
	modified:   orpsoc/simulator/modelsim.py
	modified:   orpsoc/simulator/simulator.py
	modified:   orpsoc/simulator/verilator.py
	modified:   orpsoc/utils.py