label: Always respect width-chars and max-width-chars

Not just when labels are set to ellipsize or wrap.

https://bugzilla.gnome.org/show_bug.cgi?id=647284

gtk/gtklabel.c

@@ -3081,7 +3081,7 @@ get_label_width (GtkLabel *label,
    *    request was provided.
    */
 
-  if (priv->ellipsize || priv->wrap)
+  if (priv->ellipsize || priv->wrap || priv->width_chars > 0 || priv->max_width_chars > 0)
     {
       *minimum = char_pixels * MAX (priv->width_chars, ellipsize_chars);