bug#3456: 23.0.94; character duplicated when input with MS Japanese IME

In *scratch* buffer, use MS Japanese IME to enter 'w' 'a' 't' 'a' 's' 'h' 'i'.
Then press enter twice.
The *scratch* buffer got 2 '私' characters.


In GNU Emacs 23.0.94.1 (i386-mingw-nt6.0.6001)
 of 2009-05-24 on SOFT-MJASON
Windowing system distributor `Microsoft Corp.', version 6.0.6001
configured using `configure --with-gcc (3.4)'

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: CHT
  value of $XMODIFIERS: nil
  locale-coding-system: cp950
  default-enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  recentf-mode: t
  display-time-mode: t
  display-battery-mode: t
  desktop-save-mode: t
  cua-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
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  size-indication-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
<down-mouse-1> <mouse-1> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<menu-bar> <help-menu> <about-emacs> <help-echo> <down-mouse-1>
<mouse-1> <help-echo> <down-mouse-1> <help-echo> <drag-mouse-1>
<help-echo> <down-mouse-1> <mouse-1> C-x b s c r a
<return> <language-change> <M-kanji> 私 私 <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <menu-bar> <help-menu>
<send-emacs-bug-report>

Recent messages:
Loading cperl-mode...done
PerlySense elisp files  at
(C:\strawberry\perl\site\lib\Devel\PerlySense\external) according to
perly_sense, loading...
Loading c:/strawberry/perl/site/lib/Devel/PerlySense/external/emacs/perly-sense.el
(source)...done
Loading c:/Users/yj_lee/AppData/Roaming/.emacs.d/elpa/package.el (source)...done
Loading highlight-parentheses...done
Wrote d:/.emacs.desktop.lock
Desktop: 3 buffers restored.
For information about GNU Emacs and the GNU system, type C-h C-a.
Loading c:/Users/yj_lee/AppData/Roaming/.emacs.d/elpa/eproject-0.3/eproject.cfg...done
For information about GNU Emacs and the GNU system, type C-h C-a.