bug#22090: Isearch is sluggish and eventually refuses further service with "[Too many words]".

[Eli Zaretskii]

> From: Random832 <random832@fastmail.com>
> Date: Fri, 4 Dec 2015 16:37:59 +0000 (UTC)
> 
> On 2015-12-04, Artur Malabarba <bruce.connor.am@gmail.com> wrote:
> > There were suggestions of projecting both the buffer and the search string
> > (which is what case folding does) but nobody has offered to do it.
> > What do you mean by "simple regexp"?
> 
> As in none of the huge character classes for folding, just the
> characters the user types (normalized to all-lowercase or
> all-uppercase for case-folding searches) but maybe e.g. "\s+"
> for lax whitespace.

You need to normalize the buffer text as well, so this must be done on
the C level.