(De)Iconify a window. Note that operating system or the user can force the position of the window.
Iconifie la taille d'une fenêtre.
_window_ : ObjGtk : any window already created.
_value_ : I : if _value_ = 1 then the window is iconified; if _value_ = 0, then the window is deiconified. Otherwise, nothing is done.
Return : ObjGtk : the same window or nil if error.