removed obsolete Drule.frees/vars_of; renamed thm_vars to thm_varnames;
removed obsolete Drule.frees/vars_of;
renamed thm_vars to thm_varnames;

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle