EDNS fixes

- Fixed interpretation of Extended RCODE (was not joining the normal and extended RCODE fields).
- Modified output of Extended RCODE in utilities.
- If BADVERS is returned, return minimal error response. (No Answer)

See merge request !289

Buffer boundaries are checked in knot_dname_wire_check(). The tested
function expects a valid dname. As a result, a memory outside the static
buffer is accessed.

_BSD_SOURCE is deprecated since glibc 2.20

Robert Edmonds authored 10 years ago and Jan Včelák committed 10 years ago

protobuf-c 1.0.0 added a new 'allocator' field to ProtobufCBufferSimple
that controls memory allocation, which must be NULL in order to request
the default system allocator. Allocating ProtobufCBufferSimple objects
on the stack without zeroing the entire object can result in
protobuf-c's memory allocation functions dereferencing a garbage
pointer.

Signed-off-by: Jan Vcelak <jan.vcelak@nic.cz>

See merge request !287