Add wxDataFormat GetMatchingPair() which wxGTK and wxMSW already had under different names

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@58260 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/dnd.h

@@ -36,9 +36,11 @@ public:
     virtual wxDragResult OnData(wxCoord x, wxCoord y, wxDragResult def);
     virtual bool GetData();
 
+    // Can only be called during OnXXX methods.
+    wxDataFormat GetMatchingPair();
 
     // implementation
-  
+    
     GdkAtom GtkGetMatchingPair();
 
     void GtkRegisterWidget( GtkWidget *widget );