Implemended column header mouse clicks.

Ascending/descending sorting.
  Setting the little arrow indicator for ascending
    and desceding sorting.
  Generic stubs.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@41659 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/generic/dataview.h

@@ -224,7 +224,11 @@ public:
     virtual void SetBitmap( const wxBitmap &bitmap );
     
     virtual void SetAlignment( wxAlignment align );
+    
+    virtual void SetSortable( bool sortable );
+    virtual bool GetSortable();
     virtual void SetSortOrder( bool ascending );
+    virtual bool IsSortOrderAscending();
 
     virtual int GetWidth();