Patch for Nmap's parallel DNS resolver

Current implementation of Nmap uses a parallel DNS resolver, which allows it to quickly resolve various DNS queries. This implementation of the resolver works well if the name server being used is listening on an IPv4 address, but returns an error if the name server is listening on an IPv6 address. To tackle this issue, I recently finished working on a patch which makes Nmap's parallel DNS resolver able to use an IPv6 name server.

I had written the patch some time back but couldn't test it, as I had difficulties in setting up a DNS server listening on an IPv6 address. Finally using dnsmasq and with the help of my friend Gabe Knezek, I was able to test the patch and submit it to Nmap. The patch was accepted and committed in r16016.