v0.27

 - Skip int64 tests if LLONG constants are not available
   (GH#35) (thanks, @plicease!)
 - Fix build on Cygwin64 (GH#37) (thanks, @plicease!)
 - Use ExtUtil::PkgConfig, if available, to detect system libffi
   (GH#36) (thanks, @plicease!)