bug#8431: 23.2; mh-folder-mode revert-buffer args

[Kevin Ryde <user42@zip.com.au>]

It looks like mh-folder-mode sets revert-buffer-function to a func of no
args, but revert-buffer will call with two args.  Eg. in an empty buffer

    M-x mh-folder-mode
    M-x revert-buffer
    =>
    Wrong number of arguments: #[nil ...]

Debugger entered--Lisp error: (wrong-number-of-arguments #[nil ...]
  mh-undo-folder(t nil)
  revert-buffer(t)
  call-interactively(revert-buffer t nil)
  execute-extended-command(nil)
  call-interactively(execute-extended-command nil nil)


I'm not smart enough to fire up mh to try it in real use, but I see
other revert-buffer-function handlers have (ignore-auto noconfirm) or
(&rest ignore) or (ignore1 ignore2), etc.


In GNU Emacs 23.2.1 (i486-pc-linux-gnu, GTK+ Version 2.20.0)
 of 2010-05-16 on raven, modified by Debian
configured using `configure  '--build' 'i486-linux-gnu' '--build' 'i486-linux-gnu' '--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib' '--localstatedir=/var/lib' '--infodir=/usr/share/info' '--mandir=/usr/share/man' '--with-pop=yes' '--enable-locallisppath=/etc/emacs23:/etc/emacs:/usr/local/share/emacs/23.2/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/23.2/site-lisp:/usr/share/emacs/site-lisp:/usr/share/emacs/23.2/leim' '--with-x=yes' '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars' 'build_alias=i486-linux-gnu' 'CFLAGS=-DDEBIAN -g -O2' 'LDFLAGS=-g' 'CPPFLAGS=''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_AU
  value of $XMODIFIERS: nil
  locale-coding-system: iso-latin-1-unix
  default enable-multibyte-characters: t