Add auto perspective correction to GUI

Add three buttons for correcting pitch, yaw, or both. Horizontal and/or
vertical tilt adjusters are updated with the automatically computed
values.

rtgui/lensgeomlistener.h

@@ -25,4 +25,5 @@ public:
     virtual void straightenRequested () = 0;
     virtual void autoCropRequested   () = 0;
     virtual double autoDistorRequested () = 0;
+    virtual void autoPerspRequested (bool corr_pitch, bool corr_yaw, double& rot, double& pitch, double& yaw) = 0;
 };