Solution: add compile check

Solution: extract constants / move to plain_common.hpp

Solution: ignore tautological-constant-compare warnings, as they
might be useless on 64 bit but they are not on 32 bit where sizeof
size_t != sizeof uint64_t

Solution: Enable VS static analyzer and core guideline checks

Solution: skip tests than can never succeed with MSVC

Solution: Use wepoll on Windows

Problem: API poller cannot be set independently from I/O thread poller, poll I/O thread poller broken on Windows

Solution: change platform definitions to separate API poller from I/O thread poller, disallow configuring poll I/O thread poller on Windows

Solution: enable warnings-as-errors

Solution: Factor the code into a different file with a well defined API and add
unit tests.

Solution: set the equivalent flag

Problem: When building libzmq with CMake, the installed libzmq.dylib
  has a relative install name (otool -D libzmq.dylib) on MacOS. This
  is a regression against building via autotools which sets an
  absolute install name. Effectively, the CMake built libzmq.dylib
  is rendered useless if installed in non-system directories and
  used in environments without explicit DYLD_LIBRARY_PATH mgmt. For
  example running any of the installed executables currently fails:
  $ /some_install_prefix/bin/inproc_lat
  dyld: Library not loaded: libzmq.5.dylib
    Referenced from: /some_install_prefix/bin/inproc_lat
    Reason: image not found
  Trace/BPT trap: 5

Solution: Best practice is to install relocatable dylibs.
  On MacOS this means setting an install name with a special prefix,
  e.g. @rpath/libzmq.dylib, and adding the relevant search paths
  to the embedded rpath list. In this patch the necessary CMake options
  are added to generate the desired relocatable dylibs. Find more
  information on: https://cmake.org/Wiki/CMake_RPATH_handling.

* Fixes issues with the PDB install rule for VS solutions

* Fix for compile PDB and linker PDB under Windows

Solution: revert the revert!

Revert "Problem: regression in 4.2.3 went unnoticed, want to release 4.2.5"

This reverts commit 5f17e26f.

Fixed gcc-related build problem resulting from `-errwarn=%all` switch.

Fixes #3012.

Solution: bump to 4.2.5

Solution: remove objects optimisation in library build (similar to #2860)
and set PUBLIC compile definitions on all static builds instead of MSVC
only.

Solution: change case of `WinSock2.h Iphlpapi.h Rpc.h` to match the
files on disk. This is only noticeable when cross-compiling from a
case-sensitive system so wouldn't get picked up in MSVC or mingw
builds running on a windows machine.

MSDN uses capitalised versions in prose and lowercase in code examples:
https://msdn.microsoft.com/en-us/library/windows/desktop/ms737629(v=vs.85).aspx

Fixes #2978, the missing library message is a little misleading.

Solution: made mtrie generic (to remove complex dependency on pipe_t),
and added some unit tests

This fixes an error with the cmake install configuration, which
attempted an invalid copy of a .pdb file on windows, when the
BUILD_SHARED option is disabled.

This adds a new cmake build option called BUILD_TESTS, that can be used
to enable/disable building of the tests. This is enabled by default.

This updates the cmake set_target_properperties usage, so that the suffix
is specified for the MinSizeRel build type.

Solution: add to list of sources

Solution: set up initial unit tests

Solution: fix CMAKE_MODULES_PATH

Solution: add clang-format to cmake, and add another travis-ci build type

all calls to target_link_libraries are now at the same location

with the rest of the CMake modules

* Changed CMake tests to use check_symbol_exists in network-related libraries on win32 instead of check_library_exists

Solution: bump changelog, ABI revision, library and packaging version

Signed-off-by: Gunther Laure <glaure@dewetron.com>

Solution: revert the objects optimisation, and go back to building
everything twice on Windows, as the static builds needs different
preprocessor definitions from the shared one, so the objects have to be
rebuilt.
Keep the optimisation for all the other platforms.
Fixes #2858

Solution: set it to CMake instead of a subfolder of share.
See cmake find_package documentation for further info.

Solution: build all the objects separately before the link step, to
avoid rebuilding when doing both static and shared builds

Solution: check for availability in CMake and autoconf before using it

* Background thread scheduling 

- add ZMQ_THREAD_AFFINITY ctx option; set all thread scheduling options
from the context of the secondary thread instead of using the main
process thread context!
- change ZMQ_THREAD_PRIORITY to support setting NICE of the background
thread when using SCHED_OTHER

Solution: add missing target_link_libraries
Fixes #2701