Center for Biological Sequence Analysis (CBS), BioCentrum-DTU, Building 208, The Technical University of Denmark, DK-2800 Lyngby, Denmark. pfh@cbs.dtu.dk <pfh@cbs.dtu.dk>|Center for Biological Sequence Analysis (CBS), BioCentrum-DTU, Building 208, The Technical University of Denmark, DK-2800 Lyngby, Denmark. pfh@cbs.dtu.dk <pfh@cbs.dtu.dk>