Fix fd_entry may reference invalid object.

fd_entries (std::vector) can reallocate underlying storage
which will render reference invalid.

Problem: zmq_ctx_term asserts with connect-before-bind and sockets with identity over inproc transport

Solution: add a zmq_assert to check if the ephemeral sockets created
to drain the queue of pending inproc connecting sockets was allocated
successfully.

Problem: zmq_ctx_term asserts with connect-before-bind and sockets with identity over inproc transport

Solution: check if the connecting inproc socket has been closed
before trying to send the identity.
Otherwise the pipe will be in waiting_for_delimiter state causing
writes to fail and the connect to assert when the context is being
torn down and the pending inproc connects are resolved.
Add test case that covers this behaviour.

Solution: add one to increase coverage

Problem: Pub socket crashes on client disconnect. 

Problem: Pub socket crashes on client disconnect.  family_entry.fd_entries [i] is modified in zmq::select_t::rm_fd()
Solution: do not copy family_entry.fd_entries [i]

Problem: documentation markup unrecognized

The effect can be seen on http://api.zeromq.org/4-2:zmq-getsockopt at
options ZMQ_USE_FD and ZMQ_RATE.

Solution: fix length of squiggly line under option title

Pollset-change the position of `pollset`

remove pollset.hpp/.cpp to src directory

Pollset

add a new poller named pollset which will get benefit of performance in AIX platform.

add a new poller named pollset which will get benefit of performance in AIX platform.

add a new poller named pollset which will get benefit of performance in AIX platform.

add a new poller named pollset which will get benefit of performance in AIX platform.

Problem: zmq_connect with IPv6 "source:port;dest:port" format is broken

Solution: allow for '[' character when doing the basic sanity check
on the TCP endpoint.
Also add unit tests for both IPv4 and IPv6 source;dest format.

Solution: add them

Solution: add a test for this use case

Solution: add disconnect and unbind calls to the test

Solution: refactor it to allow for multiple functionalities to be
tested

Problem: source conatins tabs and trailing spaces

Solution: remove them

Solution: replace tabes with spaces

Problem: MinGW cross compile is failed on Linux

Solution: Use only lower case for header file name.

We can find "wincrypt.h" by "WinCrypt.h" on Windows because Windows uses
case insensitive file system. But we can't find "wincrypt.h" by
"WinCrypt.h" on Linux Because Linux uses case sensitive file system.

Problem: Missing newline in printf statement

Solution: Add "\n" at end of format string.

Problem: scoped optional mutex lock caused unit tests to fail

Solution: Add a scope that scopegurad unlocks the mutex
 before the object instance deletes itself and wants to unlock
a locked mutex

Problem: socket_base uses macros for mutex lock and unlock

Solution: add a lock guard that takes optional a mutex and use it

Problem: CMake build from dist tarball broken