File locking is confused if hostname contains an @ sign

[Ulrich Mueller]

Hi,

the downstream bug at <http://bugs.gentoo.org/359415> gave me a
headache, until I realised that the user's hostname contained an @
sign. This confuses the file-locked-p function (or rather the
underlying current_lock_owner) because it will split user and host
at the wrong point.

Of course, anything other than a-z, 0-9 and hyphen is illegal in
hostnames (by RFC 952). But maybe, in spite of this, could something
be done about the problem?

For example, an easy change would be to convert @ signs to hyphens at
the end of function init_system_name. (Space and tab chars are already
being converted there.)

Alternatively, init_system_name could just error out, which would
still be better than the current behaviour.

Ulrich