Merge pull request #738 from ricnewton/master

Fix race condition on shutdown
Modified the zmq_setsockopt documentation to include the ZMQ_ROUTER_HANDOVER option
Merge pull request #739 from mbarbisan/master

Modified the zmq_setsockopt documentation to include the ZMQ_ROUTER_HAND...
Fix for issue 574
Merge pull request #740 from hintjens/master

Fix for issue 574
Simplified error handling for make_fdpair on Windows
Simplified fdpair reset after fork
Fixing issue #583. Using low resolution timer for clock::now_ms
Merge pull request #742 from psl-felipefarinon/master

Fixing issue #583. Using low resolution timer for clock::now_ms
Add test case for many sockets
Merge remote-tracking branch 'upstream/master'
Merge pull request #741 from hintjens/master

Simplified error handling for make_fdpair on Windows
Merge branch 'master' of https://github.com/zeromq/libzmq