* Modified grammar/parser slightly.
  Was: 'if assignExpr then assignExpr else assignExpr'
  Is:  'if assignExpr then expr else expr'
* Added compile.[ch].  Compilation is in its infancy.  Can only
  compile 'if/then/else', number, tuple-append: ',',
  sequence: ';', and 'null'.
* Added repl.c to tie everything together (final repl will be
  more complete).