Specifically:

* zmq_event_t should not be used internally in libzmq, it was
  meant to be an outward facing structure.

* In 4.x, zmq_event_t does not correspond to monitor events, so
  I removed the structure entirely.

* man page for zmq_socket_monitor is incomplete and the example
  code was particularly nasty.

* test_monitor.cpp needed rewriting, it was not clean.

For exchanging tokens.

E.g., both client and server need to produce and process GSSAPI tokens.

This bug is caused by fq which can terminate pipe before sending all
frames of a message first. So sometimes two messages were mixed and this
confused ZAP handler.

This patch just modifies one pipe parameter so that socket consumes all
messages before dropping the pipe.

On Solaris 8, 9, 10/SPARC, iov_base is of type caddr_t which is char *. The Sun C++ compiler errors with "Cannot assign void* to char*". Using a static case to override this. On Solaris 11, HP-UX, AIX, and RHEL, iov_base is void * so no issues there. This seems a rather hackish solution so open to something better.

zmq.h requires definitions from platform.hpp so include platform.hpp before zmq.h. This is only an intermediate fix though. zmq.h should not require definitions from platform.hpp because platform.hpp is not installed. So, when zmq.h wants to include <inttypes.h> on ZMQ_HAVE_SOLARIS || ZMQ_HAVE_OPENVMS, it will not and fall back to #include <stdint.h> which will fail when building something like pyzmq on Solaris 8, 9/SPARC which do not have <stdint.h>

Mingw64 provides mstcpip.h and the build fails (redefinition) if the struct tcp_keepalive is redefined. Do not define the struct if __MINGW64__ is defined. Note that I had to manually pass the compile definition to cmake: -D__MINGW64__=1

* report from Richard Newton indicated previous solutions was not
  working on Windows