Don't force an icon window

We were inadvertently forcing the use of an icon window
in all cases. This patch makes it so that we once again
use a combined cursor when possible.

gtk/gtkdnd.c

@@ -2517,8 +2517,7 @@ gtk_drag_begin_internal (GtkWidget         *widget,
   if (!info->icon_window && !info->icon_helper)
     {
       info->icon_helper = gtk_drag_source_site_get_icon_helper (site);
-      set_icon_helper (info->context, info->icon_helper,
-                       0, 0, TRUE);
+      set_icon_helper (info->context, info->icon_helper, 0, 0, FALSE);
     }
 
   /* We need to composite the icon into the cursor, if we are