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

Issue 1588 : Rollback in case send fails for multipart msg

create signaler::recv_failable()

In real world usage, there have been reported signaler failures where the
eventfd read() or socket recv() system call in signaler::recv() fails,
despite having made a prior successful signaler::wait() call.

this patch creates a signaler::recv_failable() method that allows
unreadable eventfd / socket to return an error without asserting.

fix error with gcc 5.2

Solution: full is if number of msg is greater than hwm, not greater than hwm - 1

Solution: use existing check_hwm() method

Update cmake to support Visual Studio 2015

Fix typo on send documentation re: nullification

fixed zmq assertion in signaler.cpp under ubuntu

Fixed the bug which cause the application crashed when use TCP connec…
Fixes #1581 

Fixed the bug which cause the application crashed when use TCP connect to an invalid address(such as 192.168.1.255).

Fix windows cmake build

Without this change, a segmentation fault is likely to occur when using the proposed snippet of code, as `*address[size]` is equivalent to `*(address[size])`, not `(*address)[size]` as clearly intended.

Problem: drop tests on CLIENT/SERVER are misleading

- both are thread safe
- they do not accept ZMQ_SNDMORE nor ZMQ_RCVMORE

These sockets deal only with single part data (at present), so the
drop tests are misleading / inappropriate.

Solution: remove them.

Various cleanups for CLIENT-SERVER sockets

REQ-REP barely work, and DEALER-ROUTER are misnamed. As we move to
formalizing CLIENT-SERVER, we can deprecate request-reply.

Solution: move this section to the end of the man page, and mark as
"will be deprecated".