adjust handling for greek characters. fixes #3188

This fixes an error in the case conversion table and removes "normal"
greek letters from the list of special characters. Mathematical symbols
based

adjust handling for greek characters. fixes #3188

This fixes an error in the case conversion table and removes "normal"
greek letters from the list of special characters. Mathematical symbols
based on greek letters are still considered special chars.

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fix the case lookup table. #3113

This readds a whole bunch of conversions that for some reason got lost
in the refactoring. No idea what happened there.

replaced deprecated utf8 functions

For now this uses full qualified namespaces, sensible imports may come
later.

unit test for FS#2173