Add cap on internal read/write buffer for QAudioOuput(PA)

cap set to no more than 5x period size

Change-Id: If3ae244993a8929832f6724c386dac6f12ef0f03
Reviewed-by: Michael Goddard <michael.goddard@nokia.com>

src/plugins/pulseaudio/qaudiooutput_pulse.cpp

@@ -293,7 +293,7 @@ bool QPulseAudioOutput::open()
     }
     const pa_buffer_attr *buffer = pa_stream_get_buffer_attr(m_stream);
     m_periodSize = pa_usec_to_bytes(PeriodTimeMs*1000, &spec);
-    m_bufferSize = buffer->maxlength;
+    m_bufferSize = qMin(m_periodSize * 5, int(buffer->maxlength));
     m_audioBuffer = new char[buffer->maxlength];
 #ifdef DEBUG_PULSE
     qDebug() << "Buffering info:";