Relax server regex in Parser

The `RE_SERVER` in the Parser follows [RFC 952](http://www.nic.mc/information/RFC/RFC952.txt), which is officially what the IRC protocol uses. However, modern users often have hostnames based on their IP (like `192-168-0-1.ip.isp.acme.com`) which causes the parser to throw an error.

Hostnames starting with digits should be allowed (not hyphens, though). A less strict regex is unlikely to cause problems with old IRC servers, but the stricter regex **definately** causes problems for users with such IPs.