bug#17130: 24.4.50; Deficient Unicode case folding

[nbtrap]

Eli Zaretskii <eliz@gnu.org> writes:

>> M-: (compare-strings "σ" nil nil "ς" nil nil t)
>> 
>> ==> -1  ;; should be t
>
> No, because these characters are not a case pair.

They're not a case pair in Emacs, but they should compare equally under
Unicode case folding.

>> Can someone that knows a thing about Unicode and emacs case tables speak
>> to whether the latter could suffice for implementing full Unicode case
>> folding?
>
> What is "full Unicode case folding"?

Somthing that implements this:
http://www.unicode.org/Public/UNIDATA/CaseFolding.txt

And perhaps more.  I don't know, but someone on this list probably does.

If you look about a third of the way down, there's a line saying that
U+03C2 (ς) should fold into U+03C3 (σ).