anchor.diff:  (export '(%buffer-keep-binfo
             %buffer-clear-keep-binfo))
   
  -(defparameter +original-buffer-name+ "*tmp*")
  +(defparameter +primordial-buffer-name+ "*tmp*")
   
   (defclass buffer ()
     ((name
  
positive.code: (in-package :lem-base)
  
  (export '(fundamental-mode
            current-buffer
            make-buffer
            buffer
  
negative.code: 
  (defvar *current-buffer*)
  
  (defun primordial-buffer ()
    (make-buffer +primordial-buffer-name+))
  
  (defun current-buffer ()
    "現在の`buffer`を返します。"
    (unless (boundp '*current-buffer*)
      (setf *current-buffer*
            (primordial-buffer)))
    *current-buffer*)
  
  (defun (setf current-buffer) (buffer)
  