bug#22891: 25.0.92; set-fringe-mode with left fringe 0 breaks window width calculations on Mac OS (again)

[martin rudalics]

> The Emacs pretest released earlier today has a window width
> calculation problem on Mac OS X when the window left fringe is turned
> off. This bug seems similar to #18601 and #16470.
>
> To reproduce, do the following:
>
> 1. Start Emacs 25.0.92 (with -Q to avoid loading initialization file).
> 2. Execute this Elisp: (set-fringe-mode '(0 . 7))
> 3. Execute M-x ansi-term and select /bin/zsh as your shell.
> 4. Resize the frame to make it slightly wider (I used the mouse to
> make the frame one character wider).
> 5. Run 'ls' in the shell. Notice the spurious % characters printed
> everywhere. This is the bug.
>
> Setting the fringe to '(1 . 7) makes the problem go away.
>
> I noticed that the fringe needs to be set wider in Emacs 25 compared
> to 24. I used fringe '(0 . 2) in the past, but that's now too small.
> It seems that the fringe window width calculation has changed, and
> re-introduced this bug.
>
>
> In GNU Emacs 25.0.92.1 (x86_64-apple-darwin15.3.0, NS appkit-1404.34
> Version 10.11.3 (Build 15D21))
>   of 2016-03-02 built on athena.local

Sorry, this mail ended up in the wrong folder so it went by unnoticed
for such long time.  I have no idea which change could have caused this.
Could you please try to bisect to find the offending commit?

Thanks, martin