Solution: fix it

Solution: if opening an IPv6 TCP socket fails because IPv6 is not
available, try to open an IPv4 socket instead when creating and
connecting a TCP endpoint.

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: rename to ZMQ_MAXRT

This is the option name used on Windows, so easier to use and
remember.

Solution: update to 2016

Only assert on errors we know are our fault,
instead of trying to whitelist every possible network-related failure.
This makes ZeroMQ more portable to other platforms
where the possible errors are different.

In particular, the previous code would often die under iOS.

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

Solution: Move the macros to a private header.

LIBZMQ-195 allow explicitly setting sndbuf and rcvbuf to 0 (see https://support.microsoft.com/en-us/kb/201213)

Of course people still "can" distributed the sources under the
LGPLv3. However we provide COPYING.LESSER with additional grants.

Solution: specify these grants in the header of each source file.

Solution: update for 2015

Fixes #1320

It must be done this way, as WSAGetLastError returns 0 in these circumstances

(accidentially used my preferred style)

As mentioned on the mailing list, Windows may return WSAEADDRINUSE when binding
(reconnecting) to a port. Added this to the handled error codes as Pieter
suggested.

Few examples:
tcp:://192.168.0.4:55555;192.168.0.254:1234
tcp:://192.168.0.4:0;192.168.0.254:1234
tcp:://eth2:55555;192.168.0.254:1234

Crash Fix: Assertion failed: Permission denied (..\..\..\src\tcp_connecter.cpp:279) on windows 8

The window scale option carried in SYN segment is computed from socket's
receive buffer size. So we need to set this buffer size before calling
connect or bind.

- we need to switch to PLAIN according to options.mechanism
- we need to catch case when both peers are as-server (or neither is)
- and to use username/password from options, for client

This implements protocol handshake.
We still need to design and implement 1) API changes so a user
can set username and password, and 2) a mechanism for engine
to authenticate users.