1.0.7.23: delete a large block of commented-out code from seqtran.lisp

1.0.7.23: delete a large block of commented-out code from seqtran.lisp

 * This is why we have version control. (But add a comment pointing out
   that this code exists, so that people know where to look for it.)

   The code that is deleted here contains the apparent beginnings of a
   better sequence transform infrastructure: a compiler representation
   of an iteration over a sequence.