Move common effect processing code to wrapper method

- Introduce `processImpl` and `sleepImpl` methods, and adapt each effect
plugin to use them
- Use double for RMS out sum in Compressor and LOMM
- Run `checkGate` for GranularPitchShifterEffect
- Minor changes to LadspaEffect
- Remove dynamic allocations and VLAs from VstEffect's process method
- Some minor style/formatting fixes

include/DummyEffect.h

@@ -98,6 +98,7 @@ public:
 		m_originalPluginData( originalPluginData )
 	{
 		setName();
+		setDontRun(true);
 	}
 
 	~DummyEffect() override = default;
@@ -107,9 +108,9 @@ public:
 		return &m_controls;
 	}
 
-	bool processAudioBuffer( SampleFrame*, const fpp_t ) override
+	double processImpl(SampleFrame*, const fpp_t) override
 	{
-		return false;
+		return -1.0;
 	}
 
 	const QDomElement& originalPluginData() const

include/Effect.h

@@ -63,9 +63,8 @@ public:
 		return "effect";
 	}
 
-	
-	virtual bool processAudioBuffer( SampleFrame* _buf,
-						const fpp_t _frames ) = 0;
+	//! Returns true if audio was processed and should continue being processed
+	bool processAudioBuffer(SampleFrame* buf, const fpp_t frames);
 
 	inline ch_cnt_t processorCount() const
 	{
@@ -175,13 +174,19 @@ public:
 
 protected:
 	/**
-		Effects should call this at the end of audio processing
+	 * The main audio processing method that runs when plugin is not asleep
+	 *
+	 * Returns the RMS output sum for use by `checkGate`,
+	 * or -1.0 if `checkGate` should not be called
+	 */
+	virtual double processImpl(SampleFrame* buf, const fpp_t frames) = 0;
+
+	/**
+	 * Optional method that runs when plugin is sleeping (not enabled,
+	 * not running, not in the Okay state, or in the Don't Run state)
+	 */
+	virtual void sleepImpl() {}
 
-		If the setting "Keep effects running even without input" is disabled,
-		after "decay" ms of a signal below "gate", the effect is turned off
-		and won't be processed again until it receives new audio input
-	*/
-	void checkGate( double _out_sum );
 
 	gui::PluginView* instantiateView( QWidget * ) override;
 
@@ -212,6 +217,16 @@ protected:
 
 
 private:
+	/**
+		Effects should call this at the end of audio processing
+
+		If the setting "Keep effects running even without input" is disabled,
+		after "decay" ms of a signal below "gate", the effect is turned off
+		and won't be processed again until it receives new audio input
+	*/
+	void checkGate( double _out_sum );
+
+
 	EffectChain * m_parent;
 	void resample( int _i, const SampleFrame* _src_buf,
 					sample_rate_t _src_sr,