VCD file dumper

1. specify output file:

0> set hw vcd[0] file "name.vcd"

2. add locations to dump (sorry, I didn't remember correctly, bits can not be dumped yet):

0> set hw vcd[0] add pc_odr
0> set hw vcd[0] add rom[0x500a]

You can set the name of the module if you want (set hw vcd[0] module name), it will be
ucsim_vcd_0 by default.

3. start recording:

0> set hw vcd[0] start

4. run the program

5. you can suspend/resume recording:

0> set hw vcd[0] pause
0> set hw vcd[0] restart

You can create an additional recorder with "set hw vcd[0] new id" and setup it with "set
hw vcd[id] ..." commands ("id" must be a number).

6. stop recording and close the vcd file:

0> set hw vcd[0] stop

After "stop", you have to specify a new file, because "start" overwrites the old one!

For examine, I use gtkwave on linux.