whiteknight/frontend_parrot2 branch ready for testing

[Andrew Whitworth]

plobsing has been doing a lot of kick-ass work on the
whiteknight/frontend_parrot2 branch in the past few days, and it's
ready for general testing. This branch rewrites the parrot executable
to bootstrap into a PIR code frontend earlier. In the
frontend/parrot2/ folder in the repo, there is a main.c file and a new
prt0.pir file (generated from prt0.winxed) which is the new entry
point.  The old Parrot executable is built as "parrot_old", for
comparison purposes.

Startup performance should be almost identical, except in programs
with many :init subs, then performance should be a little better.
Programs using pbc_to_exe ARE NOT affected and should see no
difference.

I would really appreciate as much testing as possible. We can merge
this week if there are no major problems reported.

Thanks,

--Andrew Whitworth