adjust host regex on FreeBSD

Hi.

I used Message::Passing::Input::Syslog today.

In FreeBSD, if it is sent to the udp syslog, there seems to be when there is no hostname.
There are reports similar.
http://149.20.54.209/showthread.php?t=41703

Modify the regular expression, it has solved this problem.

Please merge this If it's ok with you.

Cheers
Tomohiro Hosaka