bug#57522: 29.0.50; Fix submenu indicator on X11 no toolkit

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: manuel@ledu-giraud.fr,  57522@debbugs.gnu.org
> Date: Fri, 02 Sep 2022 19:01:14 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > AFAIK, all the implementations of menus that use the "not
> > USE_X_TOOLKIT && not USE_GTK" version of x_menu_show from xmenu.c
> > behave the same wrt locating sub-menus.
> 
> TTY menus use xmenu.c?

No, but the TTY menu code follows that of xmenu.c closely.  And MSDOS
actually uses xmenu.c code, yes.