Fixed call to sendto() in dhcp6.c. How did it every work before?

configuration - we have to read all the MAC addresses from netlink,
not bail when we find a suitable one.

Fix thinko in dhcp_update_configs - thanks to Hartmut for spotting
that.

Get a sensible address for the default DNS server even when using a
relay.

generalising the DHCP option filter code:
don't match options against context tag  when
context->netid.net == NULL, since there's no tag then.

Build DHCPv6 by default.

First cut at man page changes for DHCPv6

introduction of dnsmasq-utils.

Update debian/rules to provide no_dhcp6 and use_lua build opts.
Log DHCPv6 information request packets.

 be a domain name instead of an IP address. This allows for
 round-robin to multiple servers, in the same way as
 --dhcp-boot.

Counted string DHCP option type printing

TODO
     hostname handling.
     update DHCP6 configs from dns
     parse domain=<domain>,<IPv6 range>
     pretty-print counted string options.
     DECLINE messages
     lease-script fro DHCPv6