wishlist: ~:* to muffle compiler notes.

[SATO shinichi]

(defun test ()
  (declare (optimize speed))
  (formatter "~:*"))

; in: DEFUN TEST
; (FORMATTER "~:*")
;
; note: forced to do GENERIC-- (cost 10)
; unable to do inline fixnum arithmetic (cost 1) because:
; The first argument is a UNSIGNED-BYTE, not a FIXNUM.
; The result is a (VALUES (INTEGER -1) &OPTIONAL), not a (VALUES FIXNUM
; &REST T).
; unable to do inline fixnum arithmetic (cost 2) because:
; The first argument is a UNSIGNED-BYTE, not a FIXNUM.
; The result is a (VALUES (INTEGER -1) &OPTIONAL), not a (VALUES FIXNUM
; &REST T).
; etc.
;
; note: forced to do FAST-IF-<-ZERO (cost 9)
; unable to do inline fixnum comparison (cost 3) because:
; The first argument is a (INTEGER -1), not a FIXNUM.
; unable to do inline fixnum comparison (cost 4) because:
; The first argument is a (INTEGER -1), not a FIXNUM.
;
; note: forced to do GENERIC-> (cost 10)
; unable to do inline fixnum comparison (cost 4) because:
; The first argument is a UNSIGNED-BYTE, not a FIXNUM.
;
; note: forced to do GENERIC-+ (cost 10)
; unable to do inline fixnum arithmetic (cost 1) because:
; The first argument is a UNSIGNED-BYTE, not a FIXNUM.
; The result is a (VALUES (INTEGER 1) &OPTIONAL), not a (VALUES FIXNUM
; &REST T).
; unable to do inline fixnum arithmetic (cost 2) because:
; The first argument is a UNSIGNED-BYTE, not a FIXNUM.
; The result is a (VALUES (INTEGER 1) &OPTIONAL), not a (VALUES FIXNUM
; &REST T).
; etc.

Formatter generates a function that uses &REST lambda list keyword for ORIG-ARGS.
This means the max length of the list ORIG-ARGS is (1- CALL-ARGUMENTS-LIMIT),
(one is for STREAM the first argument of the formatter function)
and in sbcl, (= call-arguments-limit most-positive-fixnum) is T.
So we can safely declare CUR-POSN and NEW-POSN as FIXNUM.