anchor.diff:  character encodings, coding systems and external format.
   It's all the same, but everyone likes to have his own terms...
   
  -Copyright Pascal J. Bourguignon 2005 - 2012
  +CHARACTER-SET are structures containing all the information about the
  +character set, (name, characters), the encodings, the lisp
  +external-format values, the emacs coding-system strings.
  +
  +CHARACTER-SET can be designated by string-designators containing their
  +name or aliases.
  +
  +LISP-ENCODING are CL implementation specific objects usable as
  +external-format arguments.  They wrap a character-set, and a
  +line-termination mode, and possibly other parameters
  +(encoding/decoding error handling, etc).
  +
  +EMACS-ENCODING are emacs coding systems (structured strings).
  +
  +EXTERNAL-FORMATS are usually a combination of character set and
  +line-termination (and possibly additionnal information, such as
  +encoding/decoding error handling).  Often, keywords naming the
  +character set can be used as designators for external formats.
  +
  +(open file :external-format (make-external-format
  +                                 (character-set-to-lisp-encoding \"utf-8\")
  +                                 :dos))
  +
  +(let ((cs (com.informatimago.common-lisp.cesarum.character-sets:find-character-set \"utf-8\")))
  +   (when cs
  +      (format t \";; -*- mode:lisp;coding:~A -*- ~%\" (character-set-to-emacs-encoding cs))))
  +
  +(cs-name (character-set-from-emacs-encoding \"mule-utf-8-unix\"))
  +--> \"UTF-8\"
  +
  +(character-set-to-emacs-encoding :utf-8)
  +--> \"mule-utf-8-unix\"
  +
  +(character-set-to-lisp-encoding \"utf-8\")
  +--> #<external-format :utf-8/:unix #x3020003B7F5D>
  +
  +(make-external-format
  + (character-set-for-lisp-encoding
  +  (character-set-to-lisp-encoding \"utf-8\"))
  + :dos)
  +--> #<external-format :utf-8/:dos #x30200AF3E17D>
  +
  +
  +Copyright Pascal J. Bourguignon 2005 - 2021
   This package is provided under the GNU General Public Licence.
   See the source file for details.
   "))
  
positive.code: ;;;;AUTHORS
  ;;;;    <PJB> Pascal J. Bourguignon <pjb@informatimago.com>
  ;;;;MODIFICATIONS
  ;;;;    2012-04-06 <PJB> Extracted from
  ;;;;                     com.informatimago.common-lisp.cesarum.character-sets.
  ;;;;BUGS
  ;;;;LEGAL
  ;;;;    AGPL3
  ;;;;
  ;;;;    Copyright Pascal J. Bourguignon 2012 - 2016
  ;;;;
  ;;;;    This program is free software: you can redistribute it and/or modify
  ;;;;    it under the terms of the GNU Affero General Public License as published by
  
negative.code:   "
  ENCODING:  An implementation specific object representing an encoding.
             possibly with line-termination.
  RETURN:    The character-set that correspond to this lisp-encoding ;
             the line-termination.
  "
    (values (external-format-character-encoding encoding)
  