sip_session2: for calculating hash do not load the whole file into memory

darcs-hash:20090421140821-b2873-10f50bc7e79581067c752330be7342614265b33f
sip_session2: display file size in nicer units

darcs-hash:20090421140854-b2873-40f6c2d353b5ffaddbfe65eb24202bbd4cb289ce