Improvement of FxMixer multithreading

Use dynamic building of jobqueues with dependency counting:
- At the start, each channel that has no dependencies is added automatically to the queue
- Then, after each channel is processed, it increments the dep.counter of all its recipients
- When a channel's dep.counter hits the amount of its dependencies (senders), it gets automatically added to the queue
- The queue is finished when the master channel has been processed
- Muted channels are automatically processed at the start regardless dependencies, because they don't have to care about senders, being muted

Hopefully this will improve Fx Mixer performance.

include/FxMixer.h

@@ -57,6 +57,7 @@ class FxChannel : public ThreadableJob
 		QMutex m_lock;
 		int m_channelIndex; // what channel index are we
 		bool m_queued; // are we queued up for rendering yet?
+		bool m_muted; // are we muted? updated per period so we don't have to call m_muteModel.value() twice
 
 		// pointers to other channels that this one sends to
 		FxRouteVector m_sends;
@@ -65,7 +66,10 @@ class FxChannel : public ThreadableJob
 		FxRouteVector m_receives;
 
 		virtual bool requiresProcessing() const { return true; }
-
+		
+		QAtomicInt m_dependenciesMet;
+		void incrementDeps();
+		
 	private:
 		virtual void doProcessing( sampleFrame * _working_buffer );
 };
@@ -189,8 +193,6 @@ private:
 	void allocateChannelsTo(int num);
 	QMutex m_sendsMutex;
 
-	void addChannelLeaf( FxChannel * ch, sampleFrame * buf );
-
 	friend class MixerWorkerThread;
 	friend class FxMixerView;