• Added support for xz compression with
  Alien::Build::Plugin::Extract::ArchiveTar (gh#404)
  
• Extract negotiator (Alien::Build::Plugin::Extract::Negotiate)
  now prefers the Extract::ArchiveTar plugin for tar.xz files.
  On Windows Extract::ArchiveTar is now always used for tar.xz
  files because the BSD tar that comes with Windows can hang
  on tar.xz if xz is in the PATH (gh#403, gh#404)