When a menu self-destructs, free also the widget and struct menu.
As menus are self-destructing, it does not make sense to store the
window pointer, since we cannot clear it automatically. Therefore,
rename window_create_menu() to window_show_menu() that does not return
the window pointer. It also calls window_schedule_redraw() internally.
Fixes Valgrind reported memory leaks.
The alternative would be to explicitly destroy the menu in application's
menu callback.
Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>
6d174cff7a