Added span_ip4_address()/scan_ip4_address(),
      span_ip6_address()/scan_ip6_address(),
      span_ip6_reference()/scan_ip6_reference(),
      span_ip_address()/scan_ip_address(),
      span_domain()/scan_domain(), and
      span_host()/scan_host().

darcs-hash:20060124202709-65a35-cd21eb95284cb0b5642b0d7d870e2297d39120dc.gz