Merge pull request #30 from hintjens/master

 Cherry picking fixes from libzmq
Merge pull request #31 from hintjens/master

Backported fixes for libzmq-39 and other patches.
Merge pull request #32 from hintjens/master

Cherry picking changes from libzmq master
Merge pull request #34 from hintjens/master

Backporting fixes from master
Updated NEWS for release 4.0.2