Solution: applied clang-format

* Problem: missing test for status code 300, inadequate assertion for status code 500

Solution: add test, change assertion (currently test fails)

* Problem: gcc compiler error deprecated conversion from string constant

Solution: declare variable as const

* Problem: in case of ZAP handler returning a status code other than 200, no appropriate event is emitted

Solution: immediately emit event after receiving reply from ZAP handler

* Problem: endpoint address is not included in zap-reply monitor event

Solution: added functions to retrieve endpoint address in zmq::i_engine and zmq::session_base_t
removed unused code block in zmq::stream_engine_t::next_handshake_command

* Problem: wrong formatting

Solution: fix formatting

* Problem: test fails because of EPIPE

Solution: add EPIPE/ECONNRESET/ECONNAGAIN handling for more test cases

Solution: apply the option outside of the send/recv_enabled blocks so
that it is used for all types of UDP sockets

Linux now supports Virtual Routing and Forwarding (VRF) as per:

https://www.kernel.org/doc/Documentation/networking/vrf.txt

In order for an application to bind or connect to a socket with an
address in a VRF, they need to first bind the socket to the VRF device:

    setsockopt(sd, SOL_SOCKET, SO_BINDTODEVICE, dev, strlen(dev)+1);

Note "dev" is the VRF device, eg. VRF "blue", rather than an interface
enslaved to the VRF.

Add a new socket option, ZMQ_BINDTODEVICE, to bind a socket to a device.
In general, if a socket is bound to a device, eg. an interface, only
packets received from that particular device are processed by the socket.

If device is a VRF device, then subsequent binds/connects to that socket
use addresses in the VRF routing table.

Solution: use NULL instead to avoid build failure with older
compilers.

Solution: initialize to -1, since fd is a file descriptor (int).

Solution: initialize class variable in the same order as they are
defined.

Solution: fix it

Solution: The Coverity Static Code Analyzer was used on libzmq code and found
many issues with uninitialized member variables, some redefinition of variables
hidding previous instances of same variable name and a couple of functions
where return values were not checked, even though all other occurrences were
checked (e.g. init_size() return).

Solution: Phase I - make precompiled.hpp be first file included in every source file

Solution: fix these.