bug#13041: 24.2; diacritic-fold-search

[Drew Adams]

> > I'm surprised to see case mappings hard-coded in
> > lisp/international/characters.el instead of using the properties
> > `uppercase' and `lowercase' during creation of case tables.
> 
> My guess is that this is because the code in characters.el was written
> long before we had access to Unicode character properties in Emacs,
> and in fact before Emacs was switched to character representation
> based on Unicode codepoints.  And no one bothered to rewrite that code
> since then; volunteers are welcome.

Doesn't file CaseFolding.txt contain all the info needed?

If so, what about populating the case tables from the latest CaseFolding.txt
file at Emacs build time?  Or if no Internet access during build, populate from
a copy of the file to be distributed with Emacs.

And provide the same population code as a Lisp function, in case someone wants
to refresh an old Emacs release to use a more recent CaseFolding.txt file.

Would this make any sense?