Special lower/upper case handling

[benibela]

Some characters need special handling because they turn into multiple characters rather than one when case converting, as in "SpecialCasing.txt". E.g. when converting to lower case İ becomes something like0069 0307:

For upper case ß is the most notorious.

That should be handled in PUCUUTF*LowerCase/PUCUUTF*UpperCase.