refactored ZMQ_ROUTER_ANNOUNCE_SELF code. renamed it to ZMQ_PROBE_NEW_PEERS.
implement it for DEALER tocket.
+documentation
changed option name. +documentation changes
Fixed out-of-date reference
Packaging of ZMQ_PROBE

- Cleaned up man page a little
- Wrote test case tests/test_router_probe.cpp
Packaging on ZMQ_PROBE_ROUTER

- renamed to ZMQ_PROBE_ROUTER
Merge pull request #570 from hintjens/master

Packaging of probe function