Factor out $LANG parsing
Factor out extracting long and short language codes from $LANG into a shell library:
- /usr/local/sbin/unsafe-browser
- /usr/local/bin/tails-documentation
- also see fix locales form wrong assumption (#6001)
Parent Task: #6145
Related issues
- Related to #6001
Original created by @tails on 6142 (Redmine)