Sat Jul 26 22:34:20 EDT 2014

Interactive dtc

This needs the live language + some of the words in tethered.rkt need
to be parameterized.

(define (x form n)
  (if (zero? n)
      (syntax->datum form)
      (x (expand-once form) (sub1 n))))

So live part works fine, but hooking into the compiler is an
interesting problem.  The compiler pulls in target code, so it's
probably better that the `dtc-forth-begin' macro is imported as part
of the .fm

A major issue here is namespaces.  While everything works fine in
"module mode", in interactive mode the namespace has all the pic18
words in it, so that needs to be handled as well.

If everything happens in a separate namespace it should be fine.  So
it's not necessary to parameterize command line interpreter and
compiler: just have interaction pick things out of a different