* mm-util.el, nnultimate.el, nnweb.el, nnslashdot.el: Sync with

* mm-util.el, nnultimate.el, nnweb.el, nnslashdot.el: Sync with
	the Gnus CVS.

	* mm-util.el (mm-mime-mule-charset-alist): Move down and call
	mm-coding-system-p. Don't correct it only in XEmacs.
	(mm-charset-to-coding-system): Use mm-coding-system-p and
	mm-get-coding-system-list.
	(mm-emacs-mule, mm-mule4-p): New.
	(mm-enable-multibyte, mm-disable-multibyte,
	mm-enable-multibyte-mule4, mm-disable-multibyte-mule4,
	mm-with-unibyte-current-buffer,
	mm-with-unibyte-current-buffer-mule4): Use them.
	(mm-find-mime-charset-region): Treat iso-2022-jp.

	From  Dave Love  <fx@gnu.org>:

	* mm-util.el (mm-mime-mule-charset-alist): Make it correct by
	construction.
	(mm-charset-synonym-alist): Remove windows-125[02].  Make other
	entries conditional on not having a coding system defined for
	them.
	(mm-mule-charset-to-mime-charset): Use
	find-coding-systems-for-charsets if defined.
	(mm-charset-to-coding-system): Don't use
	mm-get-coding-system-list.  Look in mm-charset-synonym-alist
	later.  Add last resort search of coding systems.
	(mm-enable-multibyte-mule4, mm-disable-multibyte-mule4)
	(mm-with-unibyte-current-buffer-mule4): Just treat Mule 5 like
	Mule 4.
	(mm-find-mime-charset-region): Re-write.
	(mm-with-unibyte-current-buffer): Restore buffer as well as
	multibyteness.