Added z85 codec to ZMQ API

* Removed redundant Z85 code and include files from project
* Simplified use of headers in test cases (now they all just use testutil.hpp)
* Export zmq_z85_encode() and zmq_z85_decode() in API
* Added man pages for these two functions
Merge pull request #660 from hintjens/master

Added z85 codec to ZMQ API
simplify test_security_curve.cpp with zmq_z85_encode
Merge pull request #661 from lalebarde/master

simplify test_security_curve.cpp with zmq_z85_encode
Fix windows build
Merge pull request #662 from ricnewton/master

Fix windows build
Fixed random failures in test_security_plain and _curve

* ZAP handler thread was not getting time to start up
* Code now creates and binds handler socket in parent thread and
  passes the socket to the zap_handler, so this always gets the
  authentication requests.
Merge pull request #663 from hintjens/master

Fixed random failures in test_security_plain and _curve
NULL mechanism was not dealing with ZAP denials properly
Merge pull request #664 from hintjens/master

NULL mechanism was not dealing with ZAP denials properly
Added test case for NULL domains
Fixed length of domain setting
Merge pull request #665 from hintjens/master

Added test case for NULL domains
makes curve keys symetric as in libcurve + factorisation
oblige the application to explicitely set the node type for PLAIN
Merge pull request #666 from lalebarde/master

curve key names as in libcurve, symetry design, a few logic improvements
Reformatted text
Revert "oblige the application to explicitely set the node type for PLAIN"

This reverts commit 1206f4572b4b3bb405a14cc60605b75d53b819a0.
Revert "makes curve keys symetric as in libcurve + factorisation"

This reverts commit bfd472f97cad5e37fa384b687a906f515600bac4.
tests: don't listen on public ports