counter passes through dreamer-sim-chisel

This is a pretty simple example, but it does at least pass all the way
through vcddiff and produce exactly the same results.

In order to get larger designs through I'm probably going to have to
implement a whole bunch more opcodes, but I think that should be it.
Add gte opcode

I'm not entirely sure the semantics of this is correct because it's
not checking the widths of operands.  Unfortunately, I'm not entirely
sure what the semantics of narrow-width operations should be here...

At least it works for the small mod_counter example I'm going to
commit next... :).
Add mod_counter example

This is a slightly more complicated example that appears to work.  Of
course, it's not really much of a test...