renamed 'defns' to 'defs';
removed 'sigclass';
replaced parents by enclose;
exported parens, brackets, mk_list, mk_big_list, mk_pair, mk_triple;
various 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