refs #1995

Some newer versions of libc exported recvmmsg() symbol,
so it was detected even if the kernel couldn't support it.

refs #1995 @1h30m

- Turned assert in zone-load to if-block.
- Added more debug messages to zone-load.
- Added NULL check to knot_rdata_deep_free (possible NULL dereference - rdata->items).

Refs #1877

Refs #1877

Refs #1877

- Moved to separate subsections.

No \code{}.

refs #1877 @5m

refs #1877 @15m

refs #1877

- Replaced by @pxref where applicable

Refs #2002

- IPSECKEY rdata were being parsed in wrong way - two items were stored in one. This caused no problems during responding.
- Changed storing of APL rdata so that it is the same as TXT, currently, it might have caused undesired behaviour with transfered rdata or with rdata loaded from binary.

Closes #2002 @3h

Updated log messages for denied outgoing transfers.

fixes #2007 @3h

refs #1877

refs #1877

refs #1877

- Introduction fixed
- Requirements fixed
- Installation fixed partially

Refs #1997

- Reorganized groups.
- Updated main page.

refs #1996 @30m

- If node was empty no action was taken, but all RRs from node in the other tree
  have to be added to ADD section of changeset in such a case.
- Renamed and moved functions for clarity.

Divided into two parts. In first part the 'prev' pointers are
set. The second does the rest of the work. It's necessary because
the 'prev' pointers are used in search for domain names in RDATA
and may not be yet set well. This caused some rare problems.

refs #1952 @4h