* Complete redesign of command argument code. New code more closely

* Complete redesign of command argument code.  New code more closely
  resembles that of Emacs, with some differences, but most importantly
  the argument state is stored in a single object that can be passed
  around.

* Rename M-x backward-delete-char to M-x delete-backward-char to match
  Emacs.

* Add BACKUP-MODE argument to WRITE-BUFFER-INTERACTIVE and
  SAVE-BUFFER, to control the creation of backup files.

* New procedures give absolute limits of buffer, independent of
  current narrowing:
	GROUP-ABSOLUTE-START
	GROUP-ABSOLUTE-END
	MARK-ABSOLUTE-START
	MARK-ABSOLUTE-END
	BUFFER-ABSOLUTE-START
	BUFFER-ABSOLUTE-END

* New procedures
	WITH-GROUP-UNDO-DISABLED
	LAST-COMMAND-CHAR

* Extend REF-VARIABLE macro to take optional second arg: a buffer,
  meaning the buffer-local value of the variable in that buffer.

* Replace WITH-NARROWED-REGION! with the slightly more useful
  WITH-TEXT-CLIPPED.  Add new procedures TEXT-CLIP and GROUP-TEXT-CLIP
  to round out the set of text clipping procedures.