bug#11309: 24.1.50; Case problems with [:upper:] and Cyrillic, Greek

[Eli Zaretskii]

> From: Mattias Engdegård <mattiase@acm.org>
> Date: Tue, 8 Dec 2020 15:48:42 +0100
> Cc: 11309@debbugs.gnu.org
> 
> The remaining problem seems to be that the upcase table maps ß to itself, 
> which is wrong -- as long as we don't upcase ß to U+1E9E, it should not have 
> an upcase table entry at all. I'll see what can be done about that.

Why is this a problem?  AFAIR characters that don't have an upper-case
form map to themselves when downcased.  E.g.

  (upcase ?1) => ?1

Why should ß violate this convention?

> * src/regex-emacs.c (execute_charset): Add canon_table argument to
> allow expression of a correct predicate for [:upper:] and [:lower:].
> (mutually_exclusive_p, re_match_2_internal): Pass extra argument.
> * test/src/regex-emacs-tests.el (regexp-case-fold, regexp-eszett):
> New tests.  Parts of regexp-eszett still fail and are commented out.

Thanks, LGTM.