EDNS: Fixed reading of Extended RCODE.
EDNS: Separated "real" RCODEs from error codes.

Although RFC6895 defines error code space to be common for all
response errors, one of them is defined twice (BADVERS / BADSIG).
Also, only Extended RCODE from OPT RR is interpreted together with
RCODE from Header as one number. All other "RCODEs" are separate
error codes with dedicated fields (in TSIG or TKEY RRs).
EDNS: Modified output of utilities.

- Added helper function to retreive whole Extended RCODE to packet.
- RCODE in printed Header should be the Extended RCODE.
EDNS: Return error response in case of BADVERS.
Merge branch 'master' into edns-fixes
configure: add cflag to fail on implicit declaration
OS X: fix unit tests compilation
dnstap: Fix ProtobufCBufferSimple usage that is incorrect as of protobuf-c 1.0.0

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>
fix warning: _BSD_SOURCE is deprecated

_BSD_SOURCE is deprecated since glibc 2.20
tests: disable knot_dname_to_str_alloc() with incomplete dname

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.
zscanner: fix empty file processing
tests: update .gitignore
utils: code unification
Makefile: cleanup code coverage execution
tests-extra: Changed server creation in events tests.
log: fixed log format.
EDNS: Added missing doxygen + minor fixes.
EDNS: Improved version test
tests-extra: fix typo in edns/version
EDNS: Minor fix in doxygen