Solution: add tests for zmq_bind, zmq_connect and zmq_z85_decode

Solution: add simple, initial tests for client and server

Solution: port the 2 new tests from oss-fuzz, and wire them up to
be ran manually with a static input in normal builds.
Add a specific configure option to use the external fuzzing engine
from oss-fuzz.

Solution: define buffers in common header

Solution: refactor in testutil.lib, so that they can be used for fuzzers too

Solution: add a new TEST_ASSERT_SUCCESS_RAW_ZERO_ERRNO macro so that
it can check explicitly for non-zero values. This will be used
for getaddrinfo().

Solution: create socket in the same thread where it is used

Solution: don't run it

Solution: Add zmq_poller_size that queries the number
of objects registered, allowing safer usages of poller
to avoid livelock situations.

ZMQ_ROUTER_NOTIFY doesn't have a context and doesn't play nice with protocols. with ZMQ_DISCONNECT_MSG we can set it to a protocol message, like DISCONNECT in majordomo. Router will send it when a peer is disconnected. Another advantage of ZMQ_DISCONNECT_MSG is that it also works on inproc.

Together with ZMQ_HEARTBEAT it allows to build very reliable protocols, and much simpler as well.

When using ZMQ_HEARTBEAT one still needs to implement application-level heartbeat in order to know when to send a hello message.
For example, with the majordomo protocol, the worker needs to send a READY message when connecting to a broker. If the connection to the broker drops, and the heartbeat recognizes it the worker won't know about it and won't send the READY msg.
To solve that, the majordomo worker still has to implement heartbeat. With this new option, whenever the connection drops and reconnects the hello message will be sent, greatly simplify the majordomo protocol, as now READY and HEARTBEAT can be handled by zeromq.

* Allow CMAKE to generate ws and wss transports
I guess there is little use of just ws transport, so by default
GnuTLS (and libsodium) are enabled

* cmake libzmq including wss transport (ubuntu 19.10 and ubuntu 19.10 + wsl 1.0)
test_security_fails (libsodium assert !?)

* updated relicense

* make external libs gnutls nss sodium optional

* #ifdef WSS classes and functions, build test*ws* only if correct libs are included, warning if libs not present

* make libsodium optional

* cmake fix tests TIPC transport

* clang-format pointed out a wrongly placed #ifdef

* GnuTLS before 3.6.7 is not safe

* msvc doesn't agree with strlen in array declaration, test_socks now at least compiles on windows

* windows: libsodium build fails, missing include dirs set by env var

* ws transport test only works when GnuTLS is found

* Fixed condition to use NSS / built in SHA1, so that test_ws_transport should now pass, also when GnuTLS is not found

Solution: Fail with error if no events are active and timeout is infinite

* Problem: boilerplate when init msg from data copy

Solution: Add zmq_msg_init_buffer to construct
a message by copying memory from buffer.

Solution: run make clang-format-diff

* add option to stop trying to reconnect on ECONNREFUSED

Solution: a new socket type, called PEER. Very similar to SERVER, but can only connect to other PEERs. Also a new zmq_connect_peer method, that connect and return a routing-id in thread-safe and atomic operation

solution: if msg is not shared or constant, mask the message in place

Solution: bump minor version number in the engine as all 3.1 features
are now implemented

Solution: if all peers of a socket are >= 3.1 use sub/cancel commands
instead of the old 0/1 messages.
For backward compatibility, move the handling of 0/1 or sub/cancel
command strings to the encoders, so that the right thing can be done
depending on the protocol version.
Do not set the command flag until the encoder, so that we can handle
the inproc case (which skips the encoder).

Solution: extract new receive_monitor_address function

Solution: add const where possible

Solution: wait for monitor to stop resp. unregister monitor before
closing monitored socket.

Problem: on POSIX systems, all tests have a timeout of 60 seconds; disabling it via ZMQ_DISABLE_TEST_TIMEOUT doesn't work anymore

Solution: remove ZMQ_DISABLE_TEST_TIMEOUT guard but add default parameter to setup_test_environment

Solution: increase number of retries when reading monitor event,
and increase timeout

Solution: increase timeout to 15 seconds

Solution: define NOMINMAX

Solution: fix handling of _starting and _terminate flags

Add tests for this situation.

Clarify documentation of zmq_ctx_shutdown and zmq_socket.

Fixes #3792

Solution: implement both PONG response and producing pings

Solution: check correct preprocessor define in test_reconnect_ivl to match the
test invocation

Solution: remove the redundant one

Solution: remove else

Solution: add const

Solution: use static_cast/reinterpret_cast instead

Solution: fix identifier names

Solution: Fix ifdef for expectation of IPC support

* Problem: if IPC enabled libzmq does not compile when in uwp build

* Problem 10.0.##### can be valid windows target versions

* Problem: No builds are triggered on uwp platform

* Problem: epoll is set before UWP platform is checked

* Problem: used wrong CMAKE_SYSTEM_NAME specifier

* Problem: build tests fails during cmake configure

* Use Win32 build step for Win32-uwp platform

* Disable compile options that produce warnings that leads to a ci fail

* winnt version is set by cmake, no need for redefinition in windows.hpp

* Eliminate all warning according Incremental and opt:icf are specified

* Prefer to disable opt flags in debug config rather than incremental linking

* CMAKE_GENERATOR should not include uwp definition

* Add release build with uwp configuration

* Problem: pointer potentially uninitialized