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.

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/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)
                   ^
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Problem: no udp/multicast support in zeromq

Problem: radio/dish class broke Windows builds

Solution: add these new classes to MSVC project files

problem: radio-dish is still hacky

problem: request socket state machine check is not running

Problem: copyright year is still 2015

Solution: update to 2016

problem: pub/sub pattern in zeromq is complicated and not thread safe

stop previous monitor socket before starting new one

avoids leaking sockets due to multiple monitor calls on one socket

Alternative: raise error (not sure what errno; EADDRINUSE?) if collision detected; force manual stop.

Family is not set when resolving NIC on android.

Make it ready to enable ipv6 for AIX or HP/UX

Fix missing headers.

Problem: build fails due to undefined INT_MAX

Solution: remove debug printf line completely

Solution: include stdint.h

Solution: include climits

Fixes #1720

truncate rc to INT_MAX for send/recv

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.

Last bits of Hurd support

Problem: typo

Solution: fix it

Problem: client over inproc receives the msg with routing id set

Problem: configure --without-documentation is clumsy