Fix for issue #121

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>
active and stopping endpoint are kept separately in nn_sock

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>
Broken synchronisation in nn_shutdown() fixed

This should fix issue #31

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