Show / Hide a close button on a window. Or get this state. The result can depend to the window manager used.
Montre ou cache le bouton fermer d'une fenêtre. Peut dépendre du gestionnaire de fenêtre (système) utilisé.
_window_ : ObjGtk : any window already created.
_value_ : I : if _value_ is at 1, the window has a close button, if _value is at 0, the window hasn't a close button. If _value_ is nil (or an other value than 0 or 1), this function returns the current state (0 or 1).
Return : I : the current state.