Update to 2.2.4
    
    - New upstream release 2.2.4 (mostly a minor bugfix release)
      - Includes various fixes for:
        - Tab-width on gtk 3.6
        - Blocksync feature
        - Scrollwheel-zoom
        - Language syntax detection
        - Character encoding detection
        - Toggle comment
        - Split view
      - Performance improved, particularly for auto-completion popup speed
      - New features include:
        - More simple search options
        - Paste special (to paste for example images from Libreoffice)
        - Control-tab to switch to the most recent document
        - Save as copy
        - pylint, cssmin, jsmin, csstidy and php_beautifier integration
      - Various language syntax definition files have also been improved
    - Drop upstreamed patch for Gnome Bug #678951
    - Bump glib2/gtk version requirements as needed
    - Revert F-15 build to gtk2 as gtk3 version there is too old
      (Gnome Bug #693255)