ZMQII-9: Check and implement speculative reads & writes

src/ypollset.cpp

@@ -29,7 +29,6 @@ zmq::ypollset_t::~ypollset_t ()
 
 void zmq::ypollset_t::signal (int signal_)
 {
-printf ("++signal\n");
     zmq_assert (signal_ >= 0 && signal_ < wait_signal);
     if (bits.btsr (signal_, wait_signal))
         sem.post (); 

src/zmq_engine.cpp

@@ -137,6 +137,12 @@ void zmq::zmq_engine_t::out_event ()
 void zmq::zmq_engine_t::revive ()
 {
     set_pollout (handle);
+
+    //  Speculative write: The assumption is that at the moment new message
+    //  was sent by the user the socket is probably available for writing.
+    //  Thus we try to write the data to socket avoiding polling for POLLOUT.
+    //  Consequently, the latency should be better in request/reply scenarios.
+    out_event ();
 }
 
 void zmq::zmq_engine_t::error ()