bug#19395: 25.0.50; Setting left fringe to 0 messes up window-width

[Eli Zaretskii]

> From: Titus von der Malsburg <malsburg@posteo.de>
> Cc: 19395@debbugs.gnu.org
> Date: Wed, 17 Dec 2014 09:18:34 -0800
> 
> I want to use the full number of available columns for displaying data
> but avoid line breaks at all cost because they would mess up the table
> layout.  That's why I need a robust way to determine the maximal number
> of characters that I can put on a line.  `term-window-width' is better
> at doing that then `window-width' because it corrects (window-width) in
> a number of special cases.  (It's not perfect, though, because like
> `window-width' it ignores the size of the font in the window and
> pretends the window is using the default size.)

Exactly.  So perhaps we need a different function, one that returns
exactly the result that you want here.