winex11.drv: Select property change events on selection request windows.

dlls/winex11.drv/clipboard.c

@@ -262,7 +262,11 @@ static Window thread_selection_wnd(void)
         w = XCreateWindow(thread_data->display, root_window, 0, 0, 1, 1, 0, CopyFromParent,
                           InputOnly, CopyFromParent, 0, NULL);
         if (w)
+        {
             thread_data->selection_wnd = w;
+
+            XSelectInput(thread_data->display, w, PropertyChangeMask);
+        }
         else
             FIXME("Failed to create window. Fetching selection data will fail.\n");
     }