anchor.diff:        (buffer-add-marker buffer marker))
       marker))
   
  -(defun make-marker-current-point (&key (kind :right-inserting) name)
  -  (make-marker (current-buffer)
  -               (current-point)
  -               :kind kind
  -               :name name))
  -
   (defun copy-marker (marker &optional kind)
     (make-marker (marker-buffer marker)
                  (copy-list (marker-point marker))
  
positive.code:   (when pointp
      (setf (marker-point marker) point))
    t)
  
  
  ;;; 同じバッファ同士かの比較は保留
  
  (defun marker= (marker1 marker2)
    (assert (eq (marker-buffer marker1)
  
negative.code: (export '(current-marker
            markerp
            make-marker
            copy-marker
            delete-marker
            marker-buffer
  