Bug#264615: Norwegian characters not allowed in hostname.

[Petter Reinholdtsen <pere@hungry.com>]

[Klaus Ade Johnstad]
> I tried setting my hostname to something including the 3 special
> Norwegian characters, and was told that the hostname was invalid (no
> surprise there), with the explanation that the hostname could only
> contain alphanumeric characters and the minussign.
> 
> Clearly the 3 special Norwegian character are alphanumeric characters,
> and the error message is misleading, and should say something to that
> affect.

The error message should probably mention the ASCII letters a to z,
the ascii minus sign and the latin digits 0-9, as this is the valid
characters list of characters for host names.  Should it mention lower
case as well?

Special national letters like æøå, and special national digits like
the arabic numbers, are not allowed even if the are "alphanumeric
characters".