1.0.12.16: sequence optimizations: FILL

1.0.12.16: sequence optimizations: FILL

* Use DEFUN instead of DEFINE-SEQUENCE-TRAVERSER for FILL: the
  dispatched to functions do all the necessary checking, and do it
  better since they know more about the types.

* New function: STRING-FILL*.

* Rewrite VECTOR-FILL* and LIST-FILL* for efficiency.

* Macros VECTOR-FILL and LIST-FILL were expanded only in VECTOR-FILL*
  and LIST-FILL* -- get rid of them.

* Compile-time dispatch to STRING-FILL*, VECTOR-FILL*, LIST-FILL*, and
  SB-SEQUENCE:FILL.

* Comment above %CHECK-VECTOR-SEQUENC-BOUNDS no longer applies, delete
  it.