Merge pull request #582 from hurtonm/master

Implement CurveZMQ message encryption and authentication
Fix small streamengine issue w/ term and handshake

Also tidy up monitor test a little.
Merge branch 'master' of git://github.com/zeromq/libzmq
Merge pull request #583 from ianbarber/master

Small stream engine issue and test_monitor tidy up
Merge pull request #584 from hurtonm/master

Fix test_disconnect_inproc to work on ILP64 systems
Prints message and exits if app tries to use CURVE without libsodium
Whitespace fix to man page
Fixed spelling in comments
Fixed compile error, needed unistd.h
Merge pull request #585 from hintjens/master

Problem: allows CURVE security even if libzmq was built without libsodium
Merge pull request #586 from hurtonm/master

Make ZAP optional for CURVE mechanism
Merge pull request #587 from hurtonm/master

Make ZAP optional for CURVE mechanism
Small cleanup in pipe.cpp