faster factorial



>     Richard> (defun k (n m) ;; (k n 1) is n!
>     Richard>   (declare (fixnum n m))
>     Richard>   (if (<= n m) n
>     Richard>     (* (k n (* 2 m))
>     Richard>        (k (- n m)(* 2 m)))))

it's also faster to compute 20000! for clisp (4 x speedup).

i'm in favor of replacing the existing factorial with this one
(assuming it doesn't break something else of course),
if we can find someone to take on the task.

robert dodier