LIBZMQ-300: free received subscription messages

mato: merge patch to close libzmq-268

mato: merge patch to close libzmq-303

mato: merge patch to close libzmq-205

With the introduction of subscription forwarding, the first message sent
on a PUB socket using a unidirectional transport (e.g. PGM) is always
lost due to the "subscribe to all" being done asynchronously.

This patch fixes the problem and also refactors the code to have a single
point where the "subscribe to all" is performed.
Signed-off-by: Martin Lucina <martin@lucina.net>

Reduce memory usage of mtrie.

Signed-off-by: Staffan Gimåker <staffan@spotify.com>

Support Epoll on cross-compile without runtime test.

Updated connector open() doc strings.

Fix for LIBZMQ-305

Throw away unexpected data received by XPUB sockets, rather than asserting

Patch from Mikko Koppanen for #LIBZMQ-301

Fix build on old-ass Linux

The cause behind the segfault was next.node being deleted but count still
being non-zero.
Signed-off-by: Staffan Gimåker <staffan@spotify.com>

Add the '-Ae' flag and check for gethrtime() on HPUX

Check if CLOCK_MONOTONIC defined before using it - if not, use
gethrtime() if it's available, otherwise fall back to the old
behavior.
Signed-off-by: AJ Lewis <aj.lewis@quantum.com>

Fixes LIBZMQ-310.
Signed-off-by: Staffan Gimåker <staffan@spotify.com>

This patch fixes the problem described in LIBZMQ-205. The assertion itself
is probably caused by previously queued POLLIN events arriving after POLLIN
has been disabled on the socket.

The following additional bugs have been fixed as part of debugging this
problem:

- pgm_receiver_t does not flush messages written to the session in all
  cases which can lead to a stalled reader. Add calls to session->flush ()
  in the appropriate places.

- ensure to restart polling when a pending message is flushed in
  activate_in ().
Signed-off-by: Martin Lucina <martin@lucina.net>

Signed-off-by: Staffan Gimåker <staffan@spotify.com>

Signed-off-by: Staffan Gimåker <staffan@spotify.com>

Opening any PGM socket gives this assertion. The problem is in
pgm_sender_t::plug() which is incorrectly testing the return value from
session::write().
Signed-off-by: Martin Lucina <martin@lucina.net>

Signed-off-by: Ivo Danihelka <ivo@danihelka.net>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

Signed-off-by: Martin Lucina <martin@lucina.net>

Signed-off-by: Martin Lucina <martin@lucina.net>

When (X)SUB socket is being shut down there may be pending
outbound subscription commands in the pipes. In such case
we want to close the socket immediately instead of waiting
for the commands to be sent.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>