Make PulseAudio implementation of QSoundEffect more robust.

It was crashing when the PulseAudio daemon was not running or was
killed.
When the connection to the daemon fails (or is terminated), it now
tries to reconnect every 30 seconds.
Sounds created before a connection loss will be recreated after
reconnection.

Task-number: QTBUG-32487
Change-Id: Ia63707aa5c70434b834b3079a9950a9b35057b26
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>

src/multimedia/audio/qsoundeffect_pulse_p.h

@@ -111,6 +111,7 @@ private Q_SLOTS:
     void sampleReady();
     void uploadSample();
     void contextReady();
+    void contextFailed();
     void underRun();
     void prepare();
     void streamReady();