AudioJack: do not use QVector in processCallback()

Using QVector involves calls to malloc & friends which are not RT safe
and thus must not be used in AudioJack::processCallback(). Instead
allocate the required array upon initialization.
(cherry picked from commit ae7a4e4c2f13432d39b13c25b66231bdd6a1cc65)

include/AudioJack.h

@@ -102,9 +102,9 @@ private:
 	QSemaphore m_stopSemaphore;
 
 	QVector<jack_port_t *> m_outputPorts;
+	jack_default_audio_sample_t * * m_tempOutBufs;
 	sampleFrameA * m_outBuf;
 
-
 	f_cnt_t m_framesDoneInCurBuf;
 	f_cnt_t m_framesToDoInCurBuf;