- Abstracted macroexpansion into a single subroutine for scheme.pl.
- Deleted (already commented) code for compiling variable
  assignments.
- Fixed broken echo file in metacircular.pl.
- Abstracted macroexpansion into a seperate subroutine in
  metacircular.pl.
- Fixed broken MACROEXPAND function in both scheme.pl and
  metacircular.pl.