A Verilator testbench
elf-loader, rsp port jtag_vpi, wb_mux parameters

elf loader update, rsp port in jtag_vpi, parameter style in wb_mux
Adding Icarus options

Copied from the de1 project. Without these options CRC errors happen
during debug. There may be some ifdefs converting X's into 0's.

modified:   systems/de0_nano_sim/de0_nano_sim.core
de0_nano_sim: remove warnings