1.0.30.17: generalize the previous COERCE optimization a bit

1.0.30.17: generalize the previous COERCE optimization a bit

 * As noted by Christophe Rhodes, this is simple enough to apply to
   non-simple one-dimensional recognizable subtypes of ARRAY. ...and
   (COERCE X 'STRING) is so tempting to write that it is worth
   optimizing too.

   Need to take some care with things like

     (COERCE X '(BIT-VECTOR (NOT SIMPLE-BIT-VECTOR)))

   though.

   Add compiler notes as well.