Small unicode problems

[jpellegrini]

(string-upcase "Gauß") => "GAUß"
(string-downcase "Σo") => "σo"
(string-downcase "OΣ") => "oσ"

But the correct would be:

(string-upcase "Gauß") => "GAUSS"
(string-downcase "Σo") => "σo"
(string-downcase "OΣ") => "oς"

(I have taken the examples from the Erlang page on Unicode, https://www.erlang.org/doc/apps/stdlib/unicode_usage.html)

I see that Bigloo and Guile does the same as STklos; Chibi and Chez do not.

[jpellegrini]

I don't rally know Unicode, but I suppose the solution would have to do with these:

• https://www.unicode.org/reports/tr44/
• https://unicode.org/Public/UCD/latest/ucd/SpecialCasing.txt
• https://unicode.org/Public/UCD/latest/ucd/CaseFolding.txt

?