Use systemd vconsole.conf and locale.conf if present
    
      Resolves rhbz#881908
    - Avoid unnecessary stat calls (from Ville Skyttä)
      Resolves rhbz#741135
    - Spelling fixes (Ville Skyttä)
    - Add a test case for rhbz#742885
    - Handle case-insensitive extlinux config files properly (from Johannes Weiner)