windows.hpp must be included first due to increases _WIN32_WINNT version

added conditional includes for unix / windows

mingw defaults with _WIN32_WINNT as 0x0502 which doesn't define inet_pton(), so add a conditional check

mingw defaults with _WIN32_WINNT as 0x0502 which doesn't define inet_pton(), so add a conditional check

Solution: parse the value set by the ZMQ_PRE_ALLOCATED_FD sockopt
when creating a new TCP socket and use it if valid.
Add new tests/test_pre_allocated_fd_tcp.cpp unit test.

Solution: parse the value set by the ZMQ_PRE_ALLOCATED_FD sockopt
when creating a new IPC socket and use it if valid.
Add new tests/test_pre_allocated_fd_ipc.cpp unit test.

Solution: add new [set|get]sockopt ZMQ_PRE_ALLOCATED_FD to allow
users to let ZMQ use a pre-allocated file descriptor instead of
allocating a new one. Update [set|get]sockopt documentation and
test accordingly.

The main use case for this feature is a socket-activated systemd
service. For more information about this feature see:
http://0pointer.de/blog/projects/socket-activation.html

Solution: replace all occurrences with `zmq_ctx_term`

Solution: remove all remaining references to `zmq_utils.h`

This commit addresses the following warnings reported on gcc 5.2.1. In
the future, this will help reduce the "noise" and help catch warnings
revealing a serious problem.

8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---
/path/to/libzmq/tests/test_stream_exceeds_buffer.cpp: In function ‘int main()’:
/path/to/libzmq/tests/test_stream_exceeds_buffer.cpp:19:9: warning: variable ‘rc’ set but not used [-Wunused-but-set-variable]
     int rc = setsockopt(server_sock, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(enable));
         ^
8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---

This commit addresses the following warnings reported on gcc 5.2.1. In
the future, this will help reduce the "noise" and help catch warnings
revealing a serious problem.

8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---
/path/to/libzmq/src/options.cpp:1048:36: warning: unused parameter ‘option_’ [-Wunused-parameter]
 bool zmq::options_t::is_valid (int option_) const
                                    ^

/path/to/libzmq/src/plain_client.cpp:146:30: warning: unused parameter ‘cmd_data’ [-Wunused-parameter]
         const unsigned char *cmd_data, size_t data_size)
                              ^

/path/to/libzmq/src/plain_client.cpp:146:30: warning: unused parameter ‘cmd_data’ [-Wunused-parameter]
         const unsigned char *cmd_data, size_t data_size)
                              ^

/path/to/libzmq/src/socket_base.cpp:1445:44: warning: unused parameter ‘group_’ [-Wunused-parameter]
 int zmq::socket_base_t::xjoin (const char *group_)
                                            ^
/path/to/libzmq/src/socket_base.cpp:1451:45: warning: unused parameter ‘group_’ [-Wunused-parameter]
 int zmq::socket_base_t::xleave (const char *group_)
                                             ^

/path/to/libzmq/src/radio.cpp:145:33: warning: unused parameter ‘msg_’ [-Wunused-parameter]
 int zmq::radio_t::xrecv (msg_t *msg_)
                                 ^
/path/to/libzmq/src/dish.cpp:164:32: warning: unused parameter ‘msg_’ [-Wunused-parameter]
 int zmq::dish_t::xsend (msg_t *msg_)
                                ^

/path/to/libzmq/tests/test_msg_ffn.cpp:32:16: warning: unused parameter ‘data’ [-Wunused-parameter]
 void ffn(void *data, void *hint) {
                ^

/path/to/libzmq/tests/test_timers.cpp:50:19: warning: unused parameter ‘timer_id’ [-Wunused-parameter]
 void handler (int timer_id, void* arg)
                   ^
8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---

This commit fixes the author warnings reported below. These tests
have originally been introduced in zeromq/libzmq@5ebfd17 and
zeromq/libzmq@5fe75f0.

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CMake Warning (dev) at tests/CMakeLists.txt:133 (message):
  Test 'test_udp' is not known to CTest.
This warning is for project developers.  Use -Wno-dev to suppress it.

CMake Warning (dev) at tests/CMakeLists.txt:133 (message):
  Test 'test_large_msg' is not known to CTest.
This warning is for project developers.  Use -Wno-dev to suppress it.
8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---

Solution: update to 2016

Solution: remove debug printf line completely

Solution: include stdint.h

to avoid overflow for large messages

send/recv still succeed for large messages,
but `zmq_msg_size` must be used to get the true size.

found.
Solution: Include the source directory

Problem: _sleep is a library function of Windows.
Solution: use sleep_

Current ZMQ_REQ_RELAXED test improvement to check that pipes are not closed
after executing two send() in a row with no recv() in between.

These sockets don't handle multipart data, so if callers send it,
they drop frames, and things break silently.

Solution: if the caller tries to use ZMQ_SNDMORE, return -1 and
set errno to EINVAL.

Solution: change zmq_poller_close(p) to zmq_poller_destroy(&p)

If we're going to add CLASS-like APIs we should use the proper
syntax; specifically 'destroy' instead of 'close', which is a
hangover from the 'ZeroMQ is like sockets' model we're slowly
moving away from.

Solution: change zmq_timers_close(p) to zmq_timers_destroy(&p)

VMCI transport allows fast communication between the Host
and a virtual machine, between virtual machines on the same host,
and within a virtual machine (like IPC).

It requires VMware to be installed on the host and Guest Additions
to be installed on a guest.

Solution: add test case