o Minor bugfixes:
    - Check return code on spawn_func() in cpuworker code, so that we don't
      think we've spawned a nonworking cpuworker and write junk to it
      forever. Fix related to bug 4345; bugfix on all released Tor versions.
      Found by "skruffy".

    - Use a pthread_attr to make sure that spawn_func() cannot return
      an error while at the same time launching a thread. Fix related
      to bug 4345; bugfix on all released Tor versions. Reported by
      "cypherpunks".