add cleanup of old error log and test-still-running files
* Cambridge (UK)http://www.cl.cam.ac.uk/Research/HVG/Isabelle/dist/* Munich (Germany)http://isabelle.in.tum.de/dist/* New Jersey (USA)http://ftp.research.bell-labs.com/dist/smlnj/isabelle/source.htmlDave MacQueen <dbm@research.bell-labs.com>