• Prefer PkgConfig::PP on MSWin32 where it is more reliable. (gh#82, gh#85)
  
• Test tar command before blindly using it (tests were already
  being made for compressed tars "tar.gz", "tar.xz", etc) (gh#86, gh#87)
  
• Tweaks to test suite to hopefully accommodate a haiku install (gh#81)
  
• Add atleast_version, exact_version and max_version properties for
  pkg-config plugins (gh#78, gh#79)