worker_next: treat wait for work_available as Sleeping, not Waiting; max_threads: simple adaptive scheme between m and 2 * m;
worker_next: treat wait for work_available as Sleeping, not Waiting;
max_threads: simple adaptive scheme between m and 2 * m;

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