bug#22147: Obsolete search-forward-lax-whitespace

[Juri Linkov]

>> I mean a char-folding customization that allows a search
>> for “ä” match “a”.  Is this already possible?
>
> Not yet.
> I do want to expose more char folding options, but I want to wait for
> emacs-25 to come out first, to see if and how people will use this feature.

char-fold-symmetric could wait for later, but we definitely need
char-fold-ad-hoc now before the release because the users should be
able to customize the default rules.