Switch to using a GitHub fork which contains (almost) all our patches
    
    - Switch to using a GitHub fork of mail-notification as upstream is dead:
      https://github.com/epienbroek/mail-notification
    - Removed (almost) all patches as they're now part of the GitHub fork
    - Removed hack to link against libX11 as a proper fix was applied in the GitHub fork
    - Fixes compatibility with evolution 3.5.3 and higher
    - Re-added the BR: gob2
    - Removed ancient obsoletes tag
    - Fixed mixed-use-of-spaces-and-tabs rpmlint warning