[Koha-patches] Fixes translated boolean syspref inversion

[Frédéric DEMIANS]

> Can you provide a test case that boils down YAML::Syck's (mis)handling
> of "yes"/"no" to its essentials.  I am leaning towards gritting my
> teeth and adding the YAML::XS dependencies, but would prefer a test
> case first.
>   

I've created bug #4465 for this and will come with a simpler solution 
avoiding adding back YAML::XS.

-- 
Frédéric DEMIANS
http://www.tamil.fr/u/fdemians.html