window: Disallow maximization for windows that can't be maximized

Windows that have minimum widths larger than the screen can't be maximized,
even though we put them in a maximized state and allow users to do so:
the window just won't change size and position. Fix this by simply not giving
the option to maximize, like what happens for non-resizable windows.

https://bugzilla.gnome.org/show_bug.cgi?id=643606