refs #160

Maximal UDP payload size is 512 B (excluding UDP header)
RFC 1035 #4.2.1

refs #159

First one falsely reported UPDATE success even though it failed to serialize.
Second issue treated journal as full when transaction failed to write all
changes. This is harmless, but it broke tests.

This is a problem with packaging, when the binary is compiled on
a machine supporting newer SSE extensions than the box where the
package is installed. Moreover, CFLAGS decisions should be up to
maintainer or the one building the software.

This is O(N) on both insert/search, but since the ACL lists are
several items long (usually), it is not an issue.
The lists are sorted from the longest prefix to the shortest, so
the first match is guaranteed to be longest prefix match.

Fixed a bug where NSID couldn't be switched off on reload, causing
malformed packets and/or extra bytes.
Since it's protected by RCU, it needs to be created on each server
reload and the old one should be freed after the RCU is synchronized.
Also removed rest of obsolete code and unified EDNS constants.

refs #137

Problem was the function is copied from another one which
always decrements the arcount and trims the TSIG RR. But with
aggregated responses, this should be stripped not from first,
but from the packet actually containing the TSIG.

refs #122

refs #118

refs #118

Either set it to 0 or comment out the statement.

Main changes:
* 'system.hostname' config option is deprecated
* 'system.identity' is used for 'id.server' and 'hostname.bind'
* 'system.version' is used for 'version.server' and 'version.bind'
* In addition, config options (and NSID) support boolean on|off
* When on, the automatic default is filled on config load:
  * FQDN hostname (or at least hostname) for NSID and system.identity
  * Version string for system.version

The config options are still turned off by default.
refs #113