Fix ztree_txn_* API to work

ztree_clone() sets ztclone->zones to valid pointer even where
it was NULL in the original ztree. This happens since malloc(0)
returns always valid pointer. This confuses _ztree_update() and
various other places as in several cases ->zones is tested
instead of ->zones_len.

Fix ztree_clone() to keep ->zones as NULL if the original had
it as NULL.
Impelement loading of DJBDNS zone files
Merge pull request #53 from fabled/djbdns-support

Djbdns support
Merge branch 'master' into dev
Refactor testsuite test data dir create/populate, add djbdns

Now always wipes out the specific testout dir, and creates
  and populates the etc/zones and etc/djbdns directories iff
  they exist for the test
add etc/djbdns to list of paths created in chroot-mode
Very basic djbdns test

Just to serve as a test of testing, feel free to delete when
  replacing with better tests.
Merge branch 'master' into dev
Merge branch 'master' into dev
update djbdns tests for new structure
Merge branch 'master' into dev
Merge branch 'master' into dev
Merge branch 'master' into dev
Merge branch 'master' into dev
Merge branch 'master' into dev
Merge branch 'master' into dev

Conflicts:
	gdnsd/Makefile.am
Merge branch 'dev' into 2.x

Conflicts:
	gdnsd/Makefile.am