- additional messages to help people debugging security errors

Has some bits commented out due to #939, now work.

Note: there is an issue in libzmq when binding/unbinding or
connecting/disconnecting (I did not investigate deeper) the
same socket several times. Even closing the socket with zero
linger, zmq_ctx_term will block. The workaround in this test
case is to close the sockets for each test step.

- also removed deprecated man pages from Makefile
- they remain in repository for reference

Windows build/packaging updates.

Cleaned up socket monitor code, tests, and man page

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.

Fix windows non-unicode build

update ZMQ_STREAM docs about connection notification

Also the portion about how to close a connection does not only apply to
servers.

Add gssapi files to msvc, use Windows Unicode APIs.

Fix build issue when missing gssapi

GSSAPI/Kerberos Security Mechanism

For exchanging tokens.

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