Draft of Bytecode PDD

[Allison Randal]

I just got off the phone with Jonathan Worthington. At YAPC::EU he
agreed to draft a PDD for Parrot's bytecode file format. He has done a
fantastic job. He's checking it in now, so everyone will have a chance
to comment. The PDD incorporates a handful of important changes that
have been discussed over the past year.

After he checks it in, he'll integrate a few updates based on things we
worked out as we talked through the PDD in the call. We also still have
a few open questions, which he'll briefly summarize in a separate message.

Thanks to Jonathan for the wonderful work!

Allison