Pika VM status...

Okay, it's nothing fancy, but I've managed to take the unfinished
Scheme code Tom wrote to demo the Pika VM and clean it up enough to
provide a simple REPL (it uses the host scheme's READ, EVAL, and WRITE
routines to do all the real work, but the looping at least is done by
Pika :-).

In addition to cleaning up the VM, I've written a very quick (and
lame) compiler based on SICP's that targets this VM.  Again, nothing
fancy, but it is enough to compile a few simple expressions to the VM.

(It's 2am now and I just started these projects about two days ago, so
forgive my excitedness over such simple work. ;-)

-jivera