[BUG] Gitk elides backslashes in author names

Here's how to reproduce the problem with git version 1.6.0.2.415.g9800c0:

    $ cd /tmp
    $ rm -rf x
    $ mkdir x
    $ cd x
    $ git init
    Initialized empty Git repository in /tmp/x/.git/
    $ touch it
    $  git commit -a --author="back\\slash <foo@bar.com>" -m "yeah"
    Created initial commit 0f65eda: yeah
     0 files changed, 0 insertions(+), 0 deletions(-)
     create mode 100644 it
    $ git log
    commit 0f65eda51f33f5c56ba61f2c9dc1c5d38baec75c
    Author: back\slash <foo@bar.com>
    Date:   Thu Oct 9 19:42:17 2008 -0700

        yeah
    $ gitk

Now note that the author appears as "backslash", not "back\slash".

You might wonder why I have backslashes in my author names: it's because I'm using git-svn, and our Subversion setup -- which uses Windows authentication -- creates names with backslashes.