bug#18195: 24.3.92; window-screen-lines is not accurate

[Eli Zaretskii]

> From: Dmitry <dgutov@yandex.ru>
> Date: Tue, 05 Aug 2014 06:00:24 +0400
> 
> If I have line-spacing set, the value the above function returns is
> smaller than the actuall number of screen lines the window can contain.
> 
> For example, when I have the current Emacs frame maximized and
> line-spacing set to 0.2, (window-screen-lines) returns 46.66(6), whereas
> there are 48 fully-visible lines in the given window and one
> partially-visible one.

Fixed in revision 117425 on the emacs-24 branch.