[project @ 2005-10-26 10:42:54 by simonmar]

[project @ 2005-10-26 10:42:54 by simonmar]
- change the type of StgRun(): now we return the Capability that the
  thread currently holds.  The return status of the thread is now
  stored in cap->r.rRet (a new slot in the reg table).

  This was necessary because on return from StgRun(), the current
  TSO may be blocked, so it no longer belongs to us.  If it is a bound
  thread, then the Task may have been already woken up on another
  Capability, so the scheduler can't use task->cap to find the
  capability it currently owns.

- when shutting down, allow a bound thread to remove its TSO from
  the run queue when exiting (eliminates an error condition in
  releaseCapability()).