Added missing socket_poller.cpp file to msvc solutions.

also fixes issue https://github.com/zeromq/libzmq/issues/1624

Acutally allow specifying interfaces as source address

Problem: libzmq appveyor build status is not visible

Solution: Add a travis like badge to the README

fixes #1622

Cmake winci fixes

problem: random byte generation on windows got stuck in an infinite loop
solution: the failure test is incorrect. Change it

problem: not all configurations were built (and some were duplicated) in
Windows CI
solution: add all correct combinations to appveyor.yml

problem: cmake added a prefix of lib to libzmq, resulting in
liblibzmq.so
solution: set an empty prefix

CTest: add all sources in tests folder to CTest

TweetNaCL: add windows randombytes implementation

CMake: use libsodium + add Windows CI

problem: zmq_pollfd is not needed anymore when zmq_poller in place.

problem: ZMQ_POLLER doesn't support polling on out

enable static libraries on mingw

honor buffer reference count in zmq::shared_message_memory_allocator:…

problem: polling on multiple sockets is complicated

Fixed for issue  #1315

fix a typo in ypipe.hpp

Fixes issue #1556