Problem: Deploying release artifacts to github is a manual process

Solution: Use travis to deploy these artifacts automatically.

The deployment is triggered by tagging on the zeromq/libzmq repository.
Of the many builds travis is checking only the default one with
libsodium and drafts disabled is used for deployment.

For now the results of `make distcheck` are deployed as well as their
md5 and sha1 hash sums. Further changes may upload a generated
Changelog as well.

Problem: Not all ancillary API methods tested

Solution:
- Add file for testing ancillary API methods and any misc internal machinery
- Add tests for zmq_version(3) and zmq_strerror(3)
- Add test file into gitignore, Autotools and CMake build files
- Increase test coverage

Note:
MSVC solution files have not been updated.

problem: sockets are not signed int on Windows

Problem: no backtrace is printed on assert

Solution: clean up and remove it

Solution: add an optional dependency on libunwind, and if present
use it to print the backtrace when zmq_abort is called.

Problem: No CMake option to set ZMQ_ACT_MILITANT

Solution:
Add CMake option called WITH_MILITANT so that it aligns with the Autotools
build infrastructure; enabling this option defines ZMQ_ACT_MILITANT, which
enables assertions should malformed requests make their way into
zmq_setsockopt(3) or zmq_getsockopt(3).

Problem: read-after-free when closing socket

Solution: use socket object's mutex before the send_reap() call that
might deallocate it

problem: timers test is flapping on windows

problem: closed poller still associated with socket

Problem: AUTHORS file is not sorted

Problem: zmq_sendiov/zmq_recviov not Deprecated

Problem: style issues with comment in zmq_poll

Solution:
As preparation for 4.2 release, move the zmq_sendiov and zmq_recviov API
methods under the Deprecated Methods section.

Note: the actual methods have NOT been deprecated yet, functionally speaking
however it is good to let API users know early. Moreover, these methods were
not ever considered stable, at least according to src/zmq.h, and have no
associated man pages.

Solution:
Wrap and clean it.

Problem: ZMQ_HAVE_TIPC option for CMake is broken

Solution:
Fix it - there was a typo in the source list variable; it should be
'cpp-sources' and not 'cpp-source'.

Problem: Not shamelessly plugged into AUTHORS

Problem: MAINTAINERS file has no purpose anymore

Solution:
Remove until such time that a new and appropriate file can replace it should
it be deemed necessary.

problem: compilation error on osx

problem: src is broken and unneeded as we have metadata

Problem: supported protocols comment is stale

problem: zeromq performance got worsen by some changes

Problem: Not all GCOV extensions in .gitignore

Solution:
Fix it.

problem: no way to enable draft on windows