Added a destroy virtual method to all source input plugin main classes

plugins/samplesource/fcdpro/fcdproinput.cpp

@@ -60,6 +60,11 @@ FCDProInput::~FCDProInput()
     closeDevice();
 }
 
+void FCDProInput::destroy()
+{
+    delete this;
+}
+
 bool FCDProInput::openDevice()
 {
     int device = m_deviceAPI->getSampleSourceSequence();

plugins/samplesource/fcdpro/fcdproinput.h

@@ -77,6 +77,7 @@ public:
 
 	FCDProInput(DeviceSourceAPI *deviceAPI);
 	virtual ~FCDProInput();
+	virtual void destroy();
 
 	virtual bool start();
 	virtual void stop();