bug#21278: char-fold isearch: space and newline still broken

[Juri Linkov]

>> Building such mode-independent features on syntax properties
>> is IME asking for trouble.
>> Stefan, WDYT?
>
> Agreed.  I'd use something like [ \t] or [ \t\n] or even [\0-\s].

Seconded.  Everyone who wants to match a newline,
still needs to customize search-whitespace-regexp
to include \n, e.g. "\\(?:\\s-\\|\n\\)+", so an explicit
list of characters would be more deterministic.