Return error on invalid PGM url instead of raising assertion.

Fix Win32 build.

Fix title on zmq_disconnect manpage.

Fix issue #370

The patch extends the internal session's API with the reset method.
This method is used to reset a session's state so that it can
handle a new connection.

Code cleanup

Fix issue #369

The bug was that after reconnect, the session did not
handle identity messages properly.

Fixed zmq_poll.txt manpage for issue #361

Code cleanup

Fix too long underline in zmq_ctx_set_monitor() docs

Rename monitor documentation source file to match zmq_ctx_set_monitor() API

Moves the monitoring infrastructure to a global zmq_ctx_set_monitor () API to avoid strict aliasing issues with function pointers and socket options.

Fixed bogus reference to zmq_ctx_put

Doc improvement: document interface omission in zmq_pgm.txt

Solaris/SunCC build fix: could not find a match for std::multimap<...>::insert(std::pair<...,...>)

The PGM transport supports the omission of the network interface to
select the default one like:

  announce.connect("epgm://eth0;239.255.128.46:64646"); // Use eth0
  announce.connect("epgm://239.255.128.46:64646"); // Use the default

Also, mention C++ in the additional community bindings of 0MQ in
zmq.txt.

Rename type zmq_monitor_fn -> zmq_monitor for a more natural callback definition API (zmq_monitor type, monitor.function callback)

Change zmq_monitor_fn type to cast between pointer-to-object and pointer-to-function in a more standards compliant way