Bug: Adapting case doesn't work with letters with accents and other special characters

[NurioHin]

Title basically explains all. When using the -a option to adapt case to the found string, it won't actually adapt letters with accents (like é, ì, û, ō and many others) or other special characters. These will be inserted with whichever case it had in replace_string.

I believe only the basic 26 alphabetical letters will adapt their case