Clean up the spec file and bring it up to modern standards.
    
      * Remove patch fuzz directive.
      * Remove buildroot directive.
      * Rearrange source unpacking.
      * Remove chmod of GNU config.* files, since git does it.
      * Don't need to remove buildroot in install section.
      * Remove clean section.
    
    Note that I didn't bump the release because there's no need to rebuild
    it this time.
    (cherry picked from commit 9cefc9cb13637c74d6d4821aa2a899ff20a56318)