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

plugins/samplesource/rtlsdr/rtlsdrinput.cpp

@@ -57,6 +57,11 @@ RTLSDRInput::~RTLSDRInput()
     closeDevice();
 }
 
+void RTLSDRInput::destroy()
+{
+    delete this;
+}
+
 bool RTLSDRInput::openDevice()
 {
     if (m_dev != 0)

plugins/samplesource/rtlsdr/rtlsdrinput.h

@@ -106,6 +106,7 @@ public:
 
 	RTLSDRInput(DeviceSourceAPI *deviceAPI);
 	virtual ~RTLSDRInput();
+	virtual void destroy();
 
 	virtual bool start();
 	virtual void stop();