Libsodium has started returning -1 in some cases.

Solution: allow and handle error returns from these calls.

Fixes #1831

Solution: socket_base_t::in_event cannot do anything useful with
return status of process_commands. Asserting is the wrong solution,
as it is entirely valid to be interrupted or for the context to be
terminated, so discard the value.

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

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

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

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

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

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

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

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

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

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

Solution: don't store it in zmq::poller_base_t::adjust_load, as the
build with Werror=unused=variable will fail otherwise.

Solution: remove statc initialization to NULL of thread.hpp pthread_t
descriptor. There is no portable way to statically initialize a
pthread_t variable.

Solution: initialise it inside an ifdef too

Solution: fix it

Problem: Several problems found by Coverity Static Analyzer

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).

Problem: Visual Studio Toolset was incorrectly set in VCXPROJ files

Solution: Corrected Toolset setting where needed and inprove compilation speed
by adding defintion of WIN32_LEAN_AND_MEAN prior to any Windows specific
include files, which skips non-essential definitions during compilation.

Bump C/C++ standard version support to C11/C++11

Solution: remove it

Solution: bump to C++11 and C11 in autoconf

Solution: use CheckCXXCompilerFlag to check for support for
-std=gnu++11

Solution: import macros to check for compiler options from
autoconf-archive into the m4 subdir.

Precompiled

Problem: tweetnacl gives many warnings on MSVC

Solution: disable the warnings on this file only

We use pragmas wrapped in compiler conditionals. This will need
extending to non-gcc/msvc compilers. We could also fix the warnings
in the code, though I suspect it's not really possible.

Solution: Phase II - made compile using precompiled header

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

Problem: VC++ gives warnings on inet_addr

Solution: in project.gyp, define _WINSOCK_DEPRECATED_NO_WARNINGS

Deprecate zmq_utils.h

instead of removing it, which breaks downstream builds.

problem: dynamic cast is causing issue when compiling for nodejs

Problem:  Windows build script requires edit for DevStudio version