Various fixes and precautions

Samplebuffer: reload all samples when samplerate changes. This is because of the way LMMS uses samples: we always resample all samples t$
LadspaEffect: some safeguards for the non-inplacebroken plugins which use the same buffer for input and output. Theoretically, if some p$
FxMixer: fix effect processing in multichannel-chains

include/SampleBuffer.h

@@ -267,7 +267,7 @@ public slots:
 	void setEndFrame( const f_cnt_t _e );
 	void setAmplification( float _a );
 	void setReversed( bool _on );
-
+	void sampleRateChanged();
 
 private:
 	void update( bool _keep_settings = false );