evdns: add DNS_OPTION_NAMESERVERS_NO_DEFAULT/EVDNS_BASE_NAMESERVERS_NO_DEFAULT - DNS_OPTION_NAMESERVERS_NO_DEFAULT Do not "default" nameserver (i.e. "127.0.0.1:53") if there is no nameservers in resolv.conf, (iff DNS_OPTION_NAMESERVERS is set) - EVDNS_BASE_NAMESERVERS_NO_DEFAULT If EVDNS_BASE_INITIALIZE_NAMESERVERS isset, do not add default nameserver if there are no nameservers in resolv.conf (just set DNS_OPTION_NAMESERVERS_NO_DEFAULT internally) Fixes: #569