Make generic wxDataViewCtrl EnsureVisible() overload non-virtual

There doesn't seem to be any reason for this method to be virtual other than
preventing "virtual function hiding" warnings from gcc, so just rename it to
have a different name than the virtual EnsureVisible() inherited from the base
class instead.

include/wx/generic/dataview.h

@@ -245,7 +245,7 @@ public:
     void SetAlternateRowColour(const wxColour& colour);
 
 protected:
-    virtual void EnsureVisible( int row, int column );
+    void EnsureVisibleRowCol( int row, int column );
 
     // Notice that row here may be invalid (i.e. >= GetRowCount()), this is not
     // an error and this function simply returns an invalid item in this case.