rm-logfiles

cleaned sig;
removed add_defns (now in drule.ML as add_defs);
removed add_sigclass;
minor internal changes;

#! /bin/sh
#rm-logfiles: remove useless files from subdirectories
rm log */make*.log */make*.log.gz
rm */test
rm */.*.thy.ML
rm */ex/.*.thy.ML
rm HOL/Subst/.*.thy.ML