Last bits of Hurd support

Problem: typo

Solution: fix it

Problem: client over inproc receives the msg with routing id set

Problem: configure --without-documentation is clumsy

It's inconsistent, and should be --with-something=yes/no. Also the
term 'documentation' is long and clumy.

Solution: use --with-docs instead.

problem: condition variable setting invalid timeout

restore check for MSC 1600 before including stdint.h

GNU/Hurd support

include tweetnacl in dists

Problem: OpenWRT Makefile still uses tarballs, now using GIT HEAD master

Problem: no support for OpenWRT

Specifically, the RedHat tools.

Solution: move this into packaging/

Solution: copy ZeroMQ packaging script from
https://github.com/vperron/openwrt-zmq-packages

Note: this is not usable as-such, needs fixing.

Add support for the RelWithDebInfo CMake configuration.

It's now possible to build Release version with pdb file.

Problem: On Windows CI, in tests/test_timers.c, "Windows.hpp" could not be found.

found.
Solution: Include the source directory

Problem: _sleep is a library function of Windows.
Solution: use sleep_

Problem: Windows CI fails due to libsodium build failure

Solution: Use stable branch of libsodium

problem: when socket is destroyed before zmq_poller is the zmq_poller is accessing a dead socket

Problem: Android build is too slow

Solution: use parallel make (-j 4) and don't build man pages.

Test for issue #1690 (ZMQ_REQ_RELAXED)

Current ZMQ_REQ_RELAXED test improvement to check that pipes are not closed
after executing two send() in a row with no recv() in between.

Fixed issue #1690 (ZMQ_REQ_RELAXED)

When using ZMQ_REQ_RELAXED and a 'send' is executed after another 'send' the
previous code would terminate the 'reply_pipe' if any.
This is incorrect as terminating the reply pipe also terminates the send pipe
as they are the same (a pipe associated with a socket is bidirectional).
Doing a terminate on the pipe sets an internal flag called out_active to false
and the pipe can no longer send messages.
Removing the 'terminate' solves the problem. Removing this call is not an issue
as the incorrect ordering of messages that could be incurred is taken care of
by the ZMQ_REQ_CORRELATE option if needed.

These sockets don't handle multipart data, so if callers send it,
they drop frames, and things break silently.

Solution: if the caller tries to use ZMQ_SNDMORE, return -1 and
set errno to EINVAL.

Problem: still one error in vcxproj files

Solution: fix and try again.

(We could start to think of using zproject to generate these build
scripts as the only difference is C/C++)

Problem: includes timer.cpp/hpp instead of timers.cpp/hpp