Problem: build broken on Fedora 30

Solution: use AC_COMPILE_IFELSE instead of AC_CHECK_FUNCS to check for
strnlen, as the latter does not work anymore.

Problem: Missing doc & unit tests for zmq_poller_fd

Solution: Add some and document it.

Solution: Add doc & unit tests

Problem: zmq_socket_monitor example did not include HANDSHAKE_SUCCEEDED event causing assert failure

 Problem: Cannot get thread safe socket fd 

Solution: add one

Solution: Add a method to get the zmq_poller's signaler fd. Then we can
associate a poller instance with every thread safe socket and use its
fd.

Problem: unused Windows-specific code in sleep_ms

Solution: remove it since sleep_ms isn't used on Windows

Add <ios> include to fix uClibc++ compilation

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Under uClibc++, streamoff is defined in <ios>. This header is needed to fix compilation.

Zeromq 3479: fixed build for QNX 6.6 with CMake

Solution: Use a toolchain file for QNX x86

Solution: added relicense agreement

Solution: libm and libsocket have to be linked explicitely

Fix Radix Tree benchmark includes when used as submodule

Solution: Add a relicense statement for Omegastick

Solution: Use CMAKE_CURRENT_LIST_DIR instead of CMAKE_SOURCE_DIR when findng includes

Problems: formatting errors in docs reported by linters

Solution: fix it

Solution: add space between OR'ed values

zmq_getsockopt.3 2472: warning [p 17, 9.5i, div '3tbd1,1', 0.5i]: can't break line
zmq_setsockopt.3 3471: warning [p 24, 1.8i, div '3tbd1,1', 0.5i]: can't break line

Problem: CI format check fails

Solution: fix it

Problem: immediate binding hardening not used by debian package

Solution: set hardening=+all in Debian packaging rules

* Some explicit endpoint type changes to support GCC 5

* ../RELICENSE/SergheiNovac.md

Improve hwm pubsub test

Solution: include sent and received counts on assertion failure

Solution: use array recv variant instead

Solution: split test cases and remove code duplication

Solution: use more specific assertion macro

Solution: replace custom code by test_bind

Relicensing grant from Ericsson