IPv6 support

[nivex]

None of the utilities can establish a connection to an IPv6 enabled reflector. This is because UDPSocket.cpp uses gethostbyname() and AF_INET exclusively. The correct way to handle a dual-stack world is to call getaddrinfo() and iterate over the returned list of structs.

First discovered using USRP2M17 to connect to ref.m17.ink.