cluebars: use GTK_MESSAGE_QUESTION for nautilus' cluebars

This removes the need of a separate style for them in the theme.

src/nautilus-trash-bar.c

@@ -223,5 +223,6 @@ nautilus_trash_bar_new (NautilusView *view)
 {
 	return g_object_new (NAUTILUS_TYPE_TRASH_BAR,
 			     "view", view,
+			     "message-type", GTK_MESSAGE_QUESTION,
 			     NULL);
 }

src/nautilus-x-content-bar.c

@@ -281,6 +281,7 @@ nautilus_x_content_bar_new (GMount *mount,
 			    const char *x_content_type)
 {
 	return g_object_new (NAUTILUS_TYPE_X_CONTENT_BAR, 
+			     "message-type", GTK_MESSAGE_QUESTION,
 			     "mount", mount,
 			     "x-content-type", x_content_type, 
 			     NULL);