Virtualize StartEditor and add implementations for the ports that can do it.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67817 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/osx/dataview.h

@@ -201,6 +201,8 @@ public:
 
  // finishes editing of custom items; if no custom item is currently edited the method does nothing
   void FinishCustomItemEditing();
+  
+  virtual void StartEditor( const wxDataViewItem & item, unsigned int column );
 
  // returns the n-th pointer to a column;
  // this method is different from GetColumn(unsigned int pos) because here 'n' is not a position in the control but the n-th