group level name cannot be accented letter

[zugschlus]

This is Debian Bug #597465

<quoting>
I tried to use the following grouping in munin.conf:

[Nyomtatók;my.printer.domain.name]

However munin correctly displayed the group name in the web statistics,
no data was shown, because the directory name has been translated
internally for the special accented character "ó".

I suggest denying accented group names or fixing the character
conversion for such cases.
</quoting>