Implement padcv

Implement padcv

State subs can now be referenced and called.  Most of the tests in
lexsub.t are now passing.  I noticed mistakes in a couple of the
tests and corrected them.  In doing so I got an assertion failure
during compilation, so the tests in question I wrapped in a skipped
string eval.

State subs are now mostly working, but there are a few things to
clean up still.