Problem: WIN32 CMAKECONFIG_INSTALL_DIR is broken

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

Problem: Debian packages are missing zmq.hpp

Problem: No Jenkinsfile

Solution: install it if available. Download it from its repo as part
of the OBS source run.
Debian and Ubuntu always ship zmq.hpp in libzmq-dev, so do the same.
In the RPM world it is in its own separate package, so don't do the
same for RPM.

Problem: DRAFT API change not in NEWS

Solution: add it

Problem: no coverage for VS2013 and VS2017

Problem: ZMQ_LINGER doc change not in NEWS

Solution: add it

Wrong ZMQ_LINGER default value

Problem: Wrong linger default value

Solution: correct documentation

Solution: use if statements to avoid building it when it's disabled

Solution: add them to Appveyor

Problems: CMake rebuilds everything twice, warnings with Tweetnacl, no autoconf option to disable Werror

Solution: add workaround until Travis really fixes the issue:
https://github.com/travis-ci/travis-ci/issues/8552

Solution: add --disable-Werror flag like the existing
--disable-pedantic or CMake's -DLIBZMQ_WERROR=OFF
Fixes #2818

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

Solution: don't redefine preprocessor macro if it's already defined in
platform.hpp

Problem: accept4 not available on all platforms

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

Problems: no NEWS for 4.2.3, missing some events docs, whitespace in header

Solution: add main features and bug fixes

Solution: add them

Solution: remove it

Problem: Build fails in Visual Studio 2008 without `stdint.h`

Problems: test_security_{zap|curve} often hangs, debian builds ignore test failures hiding issues

Solution: make test failures fail the build

Solution: set 0 linger on the sockets immediately after creating them
rather than immediately before closing them.
Running through helgrind/drd highlights a few race conditions, one of
which is the setting of linger vs checking it when closing the socket.
Work around it by setting it immediately to fix the test hangs.

Problem: test_stream_exceeds_buffer cannot be ran in parallel

Change zmq_recv to zmg_msg_recv since zmq_msg_t used there.

Solution: bind to wildcard and let the OS pick a free port instead
of using an hard-coded 12345 TCP port

add Haiku support

* link against libnetwork.so for network functions.