rm-logfiles

renamed union_iff to Union_iff
renamed power_set to Pow_iff
DiffD2: now is really a destruction rule

#! /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