bug#4417: 23.1.50; vc-hg is broken in non-English locales

When opening a file in a mercurial-controlled directory, the modeline
shows "Hg-0" instead of the revision number in my de_DE.UTF-8 locale.
Moreover, after pressing "C-x v l", the *vc-change-log* buffer is
unfontified, and standard keys (d, f) do not work there, because hg's
output is in German:

,----
| Änderung:        1587:1cdfa7c5503e
| Vorgänger:       1585:ef75fa728cca
| Nutzer:          Daniel Burrows <[email protected]>
| Datum:           Sun Jul 20 12:31:09 2008 -0700
| Zusammenfassung: Document how aptitude handles double-quotes.
`----

Setting LANG to C works around the problems.  For the reference, this is
my mercurial version:

,----
| % hg --version
| Mercurial Distributed SCM (version 1.3.1)
`----

In GNU Emacs 23.1.50.6 (i486-pc-linux-gnu, GTK+ Version 2.16.6)
 of 2009-09-12 on turtle
Windowing system distributor `The X.Org Foundation', version 11.0.10603000
configured using `configure  '--build=i486-linux-gnu' 'build_alias=i486-linux-gnu' 'CFLAGS=-DGTK_DISABLE_DEPRECATED -g -O2''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: C
  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: de_DE.UTF-8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Group

Minor modes in effect:
  gnus-undo-mode: t
  display-time-mode: t
  auto-image-file-mode: t
  show-paren-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  temp-buffer-resize-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
C-x d <M-backspace> <M-backspace> d e b <tab> a <M-backspace> 
<M-backspace> <M-backspace> a p t i <tab> <return> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <return> C-x v l M-x s e t e n v <return> L 
A N G <return> C <return> C-x o C-x k <return> <return> 
C-x c l C-x o C-x k <return> C-x o C-x v l C-x o C-z 
C-x 1 M-x g n u s <return> M-x r e p o <tab> r t - 
e m <tab> <return>

Recent messages:
Opening nnfolder server on archive...done
Reading active file from archive via nnfolder...done
Opening nnfolder server...done
No new newsgroups
Checking new news...
Opening nnfolder server on archive...done
Opening nntp server on news.gnus.org...done
Opening nntp server on news.eternal-september.org...done
Checking new news...done
Making completion list...

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