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

[Po Lu]

Manuel Giraud <manuel@ledu-giraud.fr> writes:

> Here is a patch that make the submenu indicator " >" appear with X11
> no-toolkit.

That isn't how submenus are supposed to work in the oldXMenu library.
Each submenu is actually a "pane"; you can click on an item in one pane,
which activates the next pane.  An arrow indicator doesn't make sense,
since the next pane will not be activated where the indicator points to.