The patch adds ipv6 transport support for djbdns.  It would work for
tinydns and dnscache.  It requires IPv4 mapped addresses support enabled
in the operating system (which is true for Linux and can be enabled for
the BSDs except OpenBSD).

The log format changes to log the full IPv6 addresses in a non-standard,
"flat" form, for example 00000000000000000000ffffc7fe1f01 (this is
analogous to ::ffff:199.254.31.1).

The localization format of dnscache-data was amended to support IPv6.
Instead of

  %in:192.168

you need to use the above flat form with a prepended s for IPv6.  The
IPv4 form should still work unchanged.  Note that the "data.cdb" file
format changes for this and is not compatible.  If you run an unpatched
tinydns on it, it will not recognize any of the localization data.

dnscache will only try to lookup AAAA records for finding nameservers if
the A record lookup failed.  So IPv4 is default and stays like that, to
not slow down DNS lookups by looking up all name servers as IPv6 and
failing for all of them.