moved read_int etc. to library.ML; added type 'arity';
moved read_int etc. to library.ML; added type 'arity';

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