OSX specific : Set top border for the mode buttons, when settings pages has new layouts

(when tabs bar is hidden)

+ Code cleaning for OG_CustomCtrl (delete unused input parameter from the draw_blinking_bmp())

src/slic3r/GUI/wxExtensions.hpp

@@ -298,6 +298,9 @@ public:
 
     void SetMode(const /*ConfigOptionMode*/int mode);
 
+    void set_items_flag(int flag);
+    void set_items_border(int border);
+
     void msw_rescale();
 
 private: