BCP 47 language tag should use upper case region/title case script

Deleted Component: misc

RFC4646bis uses upper case region and title case script in the language tag registry. And these formats are assumed as "canonical" representation (although parse should be done in case insensitive). BCP47 conversion code introduced in ICU 4.2 uses lower case for region/script fields in language tags, which should be modified to produce the canonical format.