Writing parameters into VCD files makes the values available to waveform
tools. This can be done easily enough by writing out a $dumpadd section
at the beginning of the file that sets the parameter values. We don't need
to track the values over change, because by definition they do not change.
This changes the typical vcd output as well, so a few of the regression tests
need to be adjusted to account for this.
Also, while tracking this down, found and fixed the vvp/README.txt documention
for the .param/x records.
By adding ivtest to the iverilog source tree, it is easier to keep
the regression test synchronized with the source that is being tested.
This should be especially helpful for PRs that add a new feature, and
have a matching ivtest PR with the regression test for that feature.
Stephen Williams