bug#18601: 24.3.94; set-fringe-mode with left fringe 0 breaks window width calculations on Mac OS

[martin rudalics]

>> If it gives good results, sure.
>
> I'm happy to submit a patch, but I never signed FSF paperwork. I can
> get that ball rolling, but it would surely be faster for one of you to
> make the one-line change. :)

Feeling responsible for the changes leading up to this problem I've
committed the changes you proposed and apparently solve the problem
as revision 117557 of the release branch.  Please have a look.

Meanwhile closing this bug, martin