Fix wrong size in memset() call.

Thanks to Dave Reisner.
Allow option number zero in encapsulated DHCP options.
Bump Debian version number.
Send TCP DNS messages in one write() call. Stops TCP stream fragmenting.

This is an optimisation, not a bugfix. Thanks to Jim Bos for spotting it.
Fix crash on SERVFAIL when --conntrack in use.
Fix regression in dhcp_lease_time utility.
Manpage typos.
Note that dhcp_lease_time and dhcp_release only work for IPv4.
--dhcp-match et al now work with BOOTP as well as DHCP.
Add --synth-domain
Allow option prefix in --synth-domain.
Check length of synth-domain prefix.
Fix FTBFS in ipset.c with old kernel headers.
Tighten checks in legal_hostname().
replace inet_addr with inet_pton() in src/option.c
Only use ourselves as default DNS server for RA if we're doing DNS.

This makes RA the same as DHCP4/6
 Handle IPv4 interface-address labels in Linux.
Fix failure to start with ENOTSOCK
Generalise --interface-name to cope with IPv6 addresses.
Debian changelog update.