IPy - class and tools for handling of IPv4 and IPv6 addresses and networks.

The IP class allows a comfortable parsing and handling for most notations
in use for IPv4 and IPv6 addresses and networks.
It was greatly inspired by RIPE's Perl module NET::IP's interface but
doesn't share the implementation.
It doesn't share non-CIDR netmasks, so funky stuff like a netmask of
0xffffff0f can't be done here.