bug#13041: 24.2; diacritic-fold-search

[Drew Adams]

> Maybe it's explained here
>    http://www.unicode.org/faq/idn.html
> in the answer to
> 
>    Q: Why does IDNA2003 map final sigma (?) to sigma (s), map 
>       eszett (ß) to "ss", and delete ZWJ/ZWNJ?
> 
> One possible interpretation of this is that mapping "ß" to "SS" would
> imply that downcasing "SS" should produce "ß" and this is 
> unwanted.

This is also covered in the Unicode Regexp spec.
http://www.unicode.org/reports/tr18/