define (empty) ~wxDataObject everywhere: apparently it's needed for AIX and not only Darwin

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_4_BRANCH@17967 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/dataobj.h

@@ -22,10 +22,8 @@ class wxDataObject : public wxDataObjectBase
 {
 public:
     wxDataObject();
-#ifdef __DARWIN__
-    virtual ~wxDataObject() { }
-#endif
-    
+    virtual ~wxDataObject();
+
     virtual bool IsSupportedFormat( const wxDataFormat& format, Direction dir = Get ) const;
 };