Problem: versions are out of date

Solution: bump ABI and revisions and changelog now that v4.3.1 is out

Problem: NEWS out of date with recent changes

Solution: update it

Problem: small formatting issue highlighted by clang

Solution: fix it with make clang-format-diff

V2 decoder overflow RCE fix

Solution: Cast the signed expression (which is always positive) to unsigned
Signed-off-by: Guido Vranken <guidovranken@gmail.com>

Solution: added relicense agreement
Signed-off-by: Guido Vranken <guidovranken@gmail.com>

Problem: pointer overflow in zmq::v2_decoder_t::size_ready leading to remote code execution (issue #3351)

Solution: refactor bounds check arithmetic such that no overflow shall occur
Signed-off-by: Guido Vranken <guidovranken@gmail.com>

Problem: unused import and inconsistent use of const

Solution: remove unused import and fix const placement.

Problem: race condition in PUSH might break atomicity

Solution: if a multi-part message cannot be delivered by a PUSH socket
because the pipe is broken mid-way, drop the rest of the frames so that
the atomicity property is not broken.

Problem: tests without test framework

Solution: migrate to unity

Problem: Android helper does not redirect pkg-config

Solution: set the appropriate options, environment variables and paths
so that the host pkg-config files are ignored, and the target ones are
used instead (if any)

Migrate more tests to Unity

Solution: migrate to unity

Problem: pkg-config file cannot be used for static linking, missing dependencies in packaging

Solution: add them so that pkg-config Requires.private is
satisfied

Solution: use requires.private, which pkg-config expands recursively
so that dependencies of dependencies can be linked against when
using pkg-config --static

Solution: use the same for both autotools and cmake

Go back to ld --version-script to hide private symbols

Solution: go back to using -Wl,--version-script.

Use ax_check_vscript.m4 from the autoconf-archive to detect support on
multiple platforms (eg Solaris ld(1) -M).

libtool -export-symbols-regexp used ld(1) --retain-symbols-file under
the hood, the latter lets some C++ weak symbols make their way into the
dynamic symbols table, along with the zmq_* interface.  The reason for
such behavior is unknown to me.

TCP_NODELAY is set prior to connecting

Solution: add it

Solution: Set TCP_NODELAY after connect()

Reference: https://mail.openvswitch.org/pipermail/ovs-dev/2014-October/290251.html

Fix a typo - lenght to length

Noticed there was a small typo in the documentation.

Problem: tests without test framework

Solution: migrate to unity

Problem: tests without test framework

Solution: migrate to unity

Switching or desactivate wifi can crash Android application

returned on Android.
Solution: Avoid killing the application, allows to take
the appropriate measures to this situation.

Platforms conditionals cleanup