yum-presto Delta RPM support needs testing

yum-presto in rawhide now is in need of widespread testing.  Presto allows yum to download Delta RPM .drpm files, which contain only the difference between your installed package and the upgraded new version.  This allows yum to update packages with significant download bandwidth and time savings.

Please help us verify that yum-presto is working properly.  Please test it with both standard yum command line and PackageKit.  Simply run yum install yum-presto.  No further configurations are necessary.  Please report any problems to Bugzilla.