Use getaddrinfo instead of gethostbyname. Hopefully this makes us compatible with...

Use getaddrinfo instead of gethostbyname.  Hopefully this makes us compatible with IPv6 and with hosts that have more than one IP address.  However, I don't know of any chess servers that have either of those properties, so I couldn't test that.  I did test that xboard still works with freechess.org and chessclub.com and that it gives an error message for invalid host names.