Seems PGE/Dumper.pbc is not used.
Another missing SC op mapping.
Replace a couple of QAST::VM with QAST::Op.
A couple more coderef op mappings.
Get rid of another QAST::VM.

Seems this is one of, if not the last QAST::VM node in code-gen that
should be portable. Of course, still a bunch of pir:: and Q:PIR uses
to go.