Update to 2.5.2
    
    - Fix test case for selecting non existing candidates for Fedora rawhide
    - Update UnicodeData.txt to current Unicode 12.0 draft
    - Update emoji data to Unicode 12.0 final for 2019
    - Update emoji annotations from CLDR
    - Initialize self.dictionary_sub_properties_prop_list = [] in self._init_properties()
      (Resolves: https://github.com/mike-fabian/ibus-typing-booster/issues/46)
    - Fix test case for case mode change
    - Improve filter for dictionary selection if langtable available
    - Add BuildRequires: gcc