renamed Multithreading.regular_interrupts to Multithreading.public_interrupts; renamed Multithreading.restricted_interrupts to Multithreading.private_interrupts; added Multithreading.sync_interrupts; Multithreading.sync_wait: more careful treatment of attributes; Multithreading.tracing: uninterruptible; Multithreading.system_out: signal within critical region, more careful sync_wait; eliminated redundant Thread.testInterrupt; Future.wait_timeout: uniform Multithreading.sync_wait; future scheduler: interruptible body (sync!), to improve reactivity; future_job: reject duplicate assignments -- system error; misc tuning;