iwhois: add some improvements (thanks gall0ws)

iwhois: add some improvements (thanks gall0ws)

patch from gall0ws:

> It's impossible to get whois right and probably nobody cares about it,
> nevertheless this small patch fixes some issues with the current version:
>
> * use a more common filter for default boilerplate (useful when
>   following the referral chain)
> * updated boilerplate for *.co.uk *.net.uk *.org.uk
> * added case *.com *.net (got it from iana.org)
> * use ARIN for IPv6 addresses
> * when unsure, check first whether whois.nic.$tld exists otherwise
>   usual fallback to InterNIC
> * fixed regexp for the referral chain (case, extra spaces or /)

- add usage handling.

--
cinap