[BUG] You can't have single quote in your username

Note how `git log` discards the ending quote character:
```
root@NBR1710R:~# git init repo
Initialized empty Git repository in /root/repo/.git/
root@NBR1710R:~# cd repo/
root@NBR1710R:~/repo# git config user.name Les Actualite\'
root@NBR1710R:~/repo# cat .git/config
[core]
        repositoryformatversion = 0
        filemode = true
        bare = false
        logallrefupdates = true
[user]
        name = Les
root@NBR1710R:~/repo# git config user.name "Les Actualite\'"
root@NBR1710R:~/repo# cat .git/config
[core]
        repositoryformatversion = 0
        filemode = true
        bare = false
        logallrefupdates = true
[user]
        name = Les Actualite\\'
root@NBR1710R:~/repo# touch foo
root@NBR1710R:~/repo# git add foo
root@NBR1710R:~/repo# git commit -m 'first'
[master (root-commit) a78e11f] first
 Committer: Les Actualite <root@NBR1710R>
Your name and email address were configured automatically based
on your username and hostname. Please check that they are accurate.
You can suppress this message by setting them explicitly. Run the
following command and follow the instructions in your editor to edit
your configuration file:

    git config --global --edit

After doing this, you may fix the identity used for this commit with:

    git commit --amend --reset-author

 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 foo
root@NBR1710R:~/repo# git log
commit a78e11ff0707bd4f1bea195735a7fc8b7ee2b9f8 (HEAD -> master)
Author: Les Actualite <root@NBR1710R>
Date:   Thu Aug 22 14:25:11 2019 +0200

    first
```

I can't test with the development tree right now, ``` root@NBR1710R:~/repo# git --version git version 2.17.1 ```