PlutoSDR input: implemented transverter feature

plugins/samplesource/plutosdrinput/plutosdrinputgui.h

@@ -72,6 +72,7 @@ private:
     void updateSampleRateAndFrequency();
     void setFIRBWLimits();
     void setSampleRateLimits();
+    void updateFrequencyLimits();
 
 private slots:
     void on_startStop_toggled(bool checked);
@@ -91,6 +92,7 @@ private slots:
     void on_gainMode_currentIndexChanged(int index);
     void on_gain_valueChanged(int value);
     void on_antenna_currentIndexChanged(int index);
+    void on_transverter_clicked();
     void updateHardware();
     void updateStatus();
     void handleInputMessages();