Test is skipped if no libsodium.
Added warning if libsodium not configured

Small code cleanup

Make ZAP optional for CURVE mechanism

Make ZAP optional for CURVE mechanism

Problem: allows CURVE security even if libzmq was built without libsodium

Fix test_disconnect_inproc to work on ILP64 systems

Small stream engine issue and test_monitor tidy up

Also tidy up monitor test a little.

Implement CurveZMQ message encryption and authentication 

Problem: code isn't setting mechanism to CURVE properly

Stop ZMTP handshake when an unexpected message comes

Clean up socket_type_string

API for CURVE configuration

Changes to sanity tag in ctx

Ignored more MSVC intermmediate files.

- ZMQ_CURVE_PUBLICKEY for clients and servers
- ZMQ_CURVE_SECRETKEY for clients
- ZMQ_CURVE_SERVERKEY for clients
- ZMQ_CURVE_SERVER for servers
- added tools/curve_keygen.c as example
- updated man pages

Implement ZMTP/3.0 CURVE handshake

Missing files in cmake generated build.

fix memory leak in ipc_listener wildcard

another iteration on ZMQ_PROBE_ROUTER

now it properly works for ROUTER