genhash: implement ipv6

`genhash --server 82.94.167.243 --port 80 --url / --use-virtualhost www.mendix.com`
MD5SUM = 8da7a70e22d536bc12fe908225e3ecdd
`genhash --server 2001:888:30a9:1::f3 --port 80 --url / --use-virtualhost www.mendix.com`
MD5SUM = 8da7a70e22d536bc12fe908225e3ecdd

`wget www.mendix.com`
`md5sum index.html`
8da7a70e22d536bc12fe908225e3ecdd  index.html