fixed warnings about pointer to integer cast

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@35708 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/dnd.cpp

@@ -506,7 +506,12 @@ GdkAtom wxDropTarget::GetMatchingPair()
     GList *child = m_dragContext->targets;
     while (child)
     {
-        GdkAtom formatAtom = (GdkAtom) GPOINTER_TO_INT(child->data);
+        // in GTK+ 1.x GdkAtom was a gulong, but now it's a pointer
+        GdkAtom formatAtom = (GdkAtom)
+#ifndef __WXGTK20__
+                             GPOINTER_TO_INT
+#endif
+                             (child->data);
         wxDataFormat format( formatAtom );
 
 #ifdef __WXDEBUG__