The svg2png icon cache is now cleared on new minor version

The `version` value from the `Options` file is compared to the harcoded
value (computed at build time) of the running application. If the major
or minor version is different, the `svg2png` folder is cleaned at
startup-time.

rtgui/rtwindow.h

@@ -53,7 +53,6 @@ private:
     {
         return !options.tabbedUI && ! (options.multiDisplayMode > 0);
     };
-    void findVerNumbers (int* numbers, Glib::ustring versionStr);
 
     bool on_expose_event_epanel (GdkEventExpose* event);
     bool on_expose_event_fpanel (GdkEventExpose* event);