bug#22009: PATCH: Use `window-total-width' in `window-splittable-p'

[Eli Zaretskii]

> Date: Wed, 25 Nov 2015 18:48:15 +0100
> From: martin rudalics <rudalics@gmx.at>
> 
>  > Following discussion on emacs-devel (thread "Window splitting issues
>  > with margins"), this patch replaces the call to `window-width' in
>  > `window-splittable-p' with `window-total-width'. This takes the window
>  > margins into account when determining if a window can be split
>  > horizontally.
> 
> If no one objects I'll check it in in a few days.

To master, right?