Merge pull request #583 from ianbarber/master

Small stream engine issue and test_monitor tidy up
Fix test_disconnect_inproc to work on ILP64 systems
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
Make ZAP optional for CURVE mechanism
Merge pull request #586 from hurtonm/master

Make ZAP optional for CURVE mechanism