moved exception capture/release to structure Exn; moved multithreading to multithreading_polyml.ML;
moved exception capture/release to structure Exn;
moved multithreading to multithreading_polyml.ML;

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