- Removed functions from zone-contents - no need for them to be public.

- Mimics BIND

Two reasons:
- There's some rare race condition in the queue implementation
- Doesn't scale and current performance is almost the same (-~2%)
- Created branch with the queue still retained for future inspection

This should be properly solved by better zone fetching API with
a) refcounting b) locking.

refs #31
fixes #30

- Added a simple list to check already inserted CNAMEs
- Removed obsolote checking functions
- Nightly test will fail, because CNAME loops will be loaded and xfr-in'd

Change-Id: Ic80408a129bf42e97b9e88392d318e89cfbad3e5

(changes in scanner intentionally skipped)

Change-Id: I6c24e78f37a6f7ad1dcb3429bb9dac14d5fb9ab9

Conflicts:
	configure.ac