Merge pull request #518 from hintjens/master

Fixes to config file handling
Initialize priority
Merge pull request #520 from mvala/master

Initialize priority
Merge pull request #521 from hintjens/master

Problem: older 4.1 libzmq's return nonsense for ZMQ_SOCKET_LIMIT
Regenerated zgossip from latest zproto
Merge pull request #522 from sappo/master

re-generated zgossip_engine.h from latest zproto
Fix 'forcing int to bool'.
Add missing zgossip dynamic lib exports.
Merge pull request #523 from evoskuil/master

Add missing dynamic lib export, fix warning.
Problem: zsys deadlocked at exit, if ZSOCK_NOCHECK was defined

The code in zsys_close was wrong; it did not close sockets when the
macro was defined (due to sockets not being tracked). This led to a
shutdown deadlock in libzmq (due to 1 or more sockets remaining open).

Solution: when ZSOCK_NOCHECK is defined, do not attempt to use list
of tracked sockets in zsys_close. Always close socket. Second, if there
are sockets remaining open, log an error but don't call zmq_term().