Re: New buffer-case-table makes search_buffer painfully slow

[Richard Stallman <rms@gnu.org>]

    Emacs 22's EQUIVALENCES table relates i, and thus I as well, to two
    more characters with character codes 331857 and 331856. On
    www.unicode.org the character look up engine couldn't find a match for
    U+51051 or U+51050 saying that most likely those codes weren't
    assigned to any characters yet.

I think this has to do with the special characters for Turkish,
lower-case i without dot and upper-case I with dot.  In Turkish,
upcasing and downcasing preserve the dot, or the absence of the dot.

I think these lines in characters.el are the cause of the problem.

  (set-downcase-syntax  ?? ?i tbl)
  (set-upcase-syntax    ?I ?? tbl)

They set up only half of what Turkish needs.
They make dotless-i upcase into I, and they make
I-with-dot downcase into i.  They can't do vice versa
because that would break things for other languages.
So they are not really useful.  We could simply delete them.

We could also add a minor mode to set up the case table all the way
for Turkish.

Would someone like to do that?