Problem: missing files from VS2008 solution

Problem: gssapi_mechanism_base_t aborts the application when it receives a message it cannot decode

Solution: generate list of sources and headers with:

 ls -1 src/*cpp | sort | sed 's|src/\(.*\)|      <File RelativePath="..\\..\\..\\..\\src\\\1" />|g'
 ls -1 src/*hpp | sort | sed 's|src/\(.*\)|      <File RelativePath="..\\..\\..\\..\\src\\\1" />|g'

and add them.

Solution: emit an ZMQ_EVENT_HANDSHAKE_FAILED_PROTOCOL event instead of using zmq_assert

Problem: Values in ZMQ_EVENT_HANDSHAKE_FAILED_* are not helpful

Solution: extracted common base class curve_mechanism_base_t

Solution: emit appropriate events

Solution: emit events at appropriate places

Solution: use check_basic_command_structure in curve_client_t::decode, also prepare other client mechanisms to use that method by rearranging inheritance hierarchy

  state of ZMQ_EVENT_HANDSHAKE_FAILED_* events

Solution: update documentation

Solution: add handshake failure events to curve_client_t

Solution: emit socket monitor events for NULL protocol errors (like CURVE)

Solution: emit socket monitor events for PLAIN protocol errors (like CURVE)

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

Problem: coverage CI job does not print test errors

Solution: run make check with VERBOSE=1

specify that groups shall be UTF8

group being a `char *` is logically a text type, which needs an encoding.

Declare in the API that groups shall be UTF8-encoded,
matching the `zmq_msg_gets` API, which is the other user-facing `char *` API,
which has the same definition.

This allows bindings to provide text-type APIs,
which they cannot do if arbitrary bytes are allowed

Problem: no relicense agreement by sigiesec

Solution: added relicense agreement

Problem: ZAP client code duplicated across mechanisms with behaviour deviations

Problem: missing flags break build of test_security_curve

Solution: replaced unreachable code by assertions and adapted uses

Solution: add testutil_security.hpp to Makefile.am

Solution: added ZAP tests for PLAIN

Solution: added ZAP tests for NULL

Solution: move relevant behavior to zap_client_t

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

Solution: as a first step, parametrize mechanism configuration in CURVE tests

Solution: unification, pulled up common behaviour to zap_client_t/zap_client_common_handshake_t

Problem: zap_msg_available duplicated between curve_server_t and plain_server_t (with deviating behaviour)

Solution: pull up into zap_client_common_handshake_t, along with handle_zap_status_code and error_detail/current_error_detail

Solution: extract into new intermediate base class zap_client_common_handshake_t

Solution: pull state enum up to zap_client_t and unify names of enum values

Solution: extract receive_and_process_zap_reply into zap_client_t and convert zap_client_t into base class of the server mechanism classes

Solution: Use zap_client_t::send_zap_request

Solution: Set more flag depending on presence of credentials

Problem: null_mechanism duplicates zap_client_t::send_zap_request\nSolution: use zap_client_t::send_zap_request

Solution: Use zap_client_t::send_zap_request

Solution: created a zap_client_t class, extracted first function send_zap_request from curve_server_t

Solution: add all the required compiler flags since the test includes
source code from the library directly