Parse nameservers from whois response.

Uglyness - we get nameservers returned as pairs of lines like:

domain.nservers.nserver.no: 1
domain.nservers.nserver.handle: ultra103.uk2.net
domain.nservers.nserver.no: 2
domain.nservers.nserver.handle: ultra104.uk2.net

Of course, as we're parsing key: value into a hash, we'd see only the last one;
so special-case this in the splitting map and shove all nameservers seen into an
arrayref we can shove into the results later.

Also replaced the stub of the parsing code I'd started writing in query_whois
with a simple call to _parse_whois_response.
Parse and store list of available TLDs.

Joker return the list of TLDs available to the reseller in the response to the
login call, so may as well parse and store it.