This reverts commit 1206f457.

curve key names as in libcurve, symetry design, a few logic improvements

Added test case for NULL domains

NULL mechanism was not dealing with ZAP denials properly

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.

Fix windows build

simplify test_security_curve.cpp with zmq_z85_encode

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

Fixed Z85 methods to be static

Support high water mark on inproc socket connect before bind.

Build didn't work if libsodium wasn't installed

Allow inproc sockets to connect before bind

Fixed overwrite in zmq_getsockopt

add exhaustive comparison in testutil bounce

On ZMQ_CURVE_xxxKEY fetches, would return 41 bytes into caller's 40-byte
buffer. Now these fetches only return 41 bytes if the caller explicitly
provides a 41-byte buffer (i.e. the option size is 41).

Fix preprocessor typoe