comment-region with prefix argument doesn't undo commenting in XML mode

[Martin Fischer <parozusa@web.de>]

Please write in English if possible, because the Emacs maintainers
usually do not have translators to read other languages for them.

Your bug report will be posted to the emacs-pretest-bug@gnu.org mailing list.

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

  8<-------------------------------------------------------------------
  Select the following XML code snippet as region.

    <Titel>"BlaBla"</Titel>
    <!-- Comment -->
    <Tag> Property="Value" </Tag>

  M-x comment-region RET yields:

    <!-- <Titel>"BlaBla"</Titel> -->
    <!-- <\!-- Comment -\-> -->
    <!-- <Tag> Property="Value" </Tag> -->

  Selecting the same region again and C-u M-x comment-region RET
  doesn't restore the original text.

    <Titel>"BlaBla"</Titel>
    <\! Comment -\-> >
    <! <Tag> Property="Value" </Tag> >
  8<-------------------------------------------------------------------

If Emacs crashed, and you have the Emacs process in the gdb debugger,
please include the output from the following gdb commands:
    `bt full' and `xbacktrace'.
If you would like to further debug the crash, please read the file
d:/aemf/emacs-22.1.90/etc/DEBUG for instructions.


In GNU Emacs 22.1.90.1 (i386-mingw-nt5.1.2600)
 of 2008-01-31 on PRETEST
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --cflags -Ic:/gnuwin32/include'

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: DEU
  locale-coding-system: cp1252
  default-enable-multibyte-characters: t

Major mode: XML

Minor modes in effect:
  encoded-kbd-mode: t
  tooltip-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  auto-compression-mode: t
  line-number-mode: t

Recent input:
C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k 
C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k 
C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k 
C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k C-k <down> 
<down> <down> <down> C-k C-k C-k C-k C-k C-k C-k C-k 
C-k C-k C-k C-k C-k C-k C-x C-s <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<menu-bar> <help-menu> <send-emacs-bug-report>

Recent messages:
("d:\\aemf\\emacs-22.1.90\\bin\\emacs.exe" "-Q" "u:/aemf/test.xml")
Loading encoded-kb...done
For information about GNU Emacs and the GNU system, type C-h C-a.
Loading sgml-mode...done
Loading regexp-opt...done
Wrote u:/aemf/test.xml
Loading emacsbug...done