Solution: move general monitoring test utilities to new testutil_monitoring

Solution: use memcpy instead of doing pointer arithmetics with casting
and dereferencing to fix the error on sparc64

Solution: do it

Solution: apply naming style

Solution: explicitly compare function pointer against NULL

Solution: override unused parameter for NULL wrapper

Solution: applied clang-format

Solution: set 0 linger on the sockets immediately after creating them
rather than immediately before closing them.
Running through helgrind/drd highlights a few race conditions, one of
which is the setting of linger vs checking it when closing the socket.
Work around it by setting it immediately to fix the test hangs.

Solution: add ZMQ_ZAP_ENFORCE_DOMAIN to hide backward incompatible
change and make it disabled by default.
In a future release that breaks API compatibility we can then switch
the default to enabled in order to achieve full RFC compatibility.

Fixes #2762

Solution: use "routing_id" instead

Solution: replace by "routing id"

receive an ERROR (probably because the connection is closed before)

Solution: wait for client-side monitor events before closing the client
socket

Fixes #2705

Solution: added tests

Solution: added test & some improvements of test utils

Solution: emit events as expected by tests, and refuse connections when
ZAP is required but no handler started

Addresses #2711 partially

Solution: added test case for NULL/PLAIN/CURVE

Solution: replace by "routing id"

Solution: add diagnostic output

Problem: test_zap_unsuccessful_status_500 and test_curve_security_with_bogus_client_credentials sometimes fail, particulary on slow/valgrind runs

Solutio: relax test assertion

Problem: no tests for client-side events for successful handshake and authentication failure in handshake

Solution: added tests for CURVE, add emitting of client-side event in curve_client_t; add ZAP code 300/500 tests for all mechanisms; suppress sending an error message for ZAP code 300

Solution: use LIBZMQ_UNUSED where necessary

Solution: redesign ZMQ_HANDSHAKE_FAILED_* events, introduce new class of ZMQ_HANDSHAKE_FAILED_AUTH events

Solution: added ZAP tests for PLAIN

Solution: added ZAP tests for NULL

Solution: Move ZAP tests to own file test_security_zap.cpp, move common code to testutil_security.hpp