V3 of performance test patches

[da...@tethera.net]

This obsoletes 

     id:1353378200-28625-1-git-send-email-david at tethera.net
     id:1353378200-28625-2-git-send-email-david at tethera.net

Thanks to Tomi for the suggestion of using xz compression; this about
halves the size of the corpus tarball.