plugin_geodns: fix the omit datacenter commit

Remove the unneeded info->auto_limit access (from my bad merge),
which can make valgrind unhappy. Also default num_auto to num_dcs
to have auto_limit like it was if auto_dc_coords is not used
(though it should not be used in that case at all).

Signed-off-by: Timo Teräs <timo.teras@iki.fi>
Fix testsuite bug w/ Net::DNS 0.68
Merge branch 'master' into dev
allow hashing emptiness
zlist->ztree refactor

Zones are now stored in a tree structure very similar
to the "ltree" used for the data of a single zone.

This allows for subzones to work "correctly", meaning
superzones always hide subzones, but the subzone data
will re-appear on deletion of the relevant superzone(s).
fix locking bug in ztree_node_grow()
s/zlist/ztree/ cleanup
copy zone serial to zone_t during finalize
ztree-level duplicate zone sorting

If more than one data source for a given zone is alive at one
moment in time (virtual time as measured by the serial
invocations of ztree_update()), they will now always be sorted.

The sort criteria is first by the zone serial number from the
SOA record, and then (if serials are equal) by the mtime
provided by the source (file mtime on disk in the rfc1035
case).  If both serial and mtime compare equally, the
most-recently updated file in terms of the realtime
ztree_update() invocation timeline wins.

Note: serial math is naive in this first version, I need to
look up how to do it properly to handle wrapping correctly.
zone sorting optimization

Don't use the two-step swap when the new copy of the zone
sorts just after the old copy, as this is effectively the
same as sorting equal.
Implement serial number math properly
fill in missing rfc1035 prefixes in log msgs
Just basic structure and notes for the djb code
fix compile error on non-Linux
typo in configure help string
Merge branch 'master' into dev
move ztree child hash into sep sub-object
liburcu for ztree zone data

This replaces the pthread_rwlock stuff with liburcu-qsbr for
fast lock-free swap-ins of new zone data, on hosts where
configure can detect liburcu-qsbr.

liburcu info: http://lttng.org/urcu

Linux: Fedora has old RPMs that work, EPEL has newer ones, both
are named userspace-rcu[-devel].

Supposedly pretty portable these days, although I had problems
getting it compiled on a Mac Lion machine for 64-bit (32-bit
explicitly with -m32 seemed to build).
chaos_response: configurable "version" string, Issue #6.
actually starting the check/prep watchers helps