Subprocess support in this version requires microcode version 11.66 or

Subprocess support in this version requires microcode version 11.66 or
later.

* Subprocess abstraction changed to use microcode's new process status
  synchronization.  The procedure `subprocess-status' causes the
  status information to be synchronized; subsequently
  `subprocess-exit-reason' returns the reason corresponding to that
  status.  Likewise, the new procedure `subprocess-status-tick'
  returns an object representing the time-stamp associated with this
  status; when the status changes, the tick is changed to a new value.
  Ticks are unique objects that are comparable using `eq?'; they are
  not ordered.

* New procedure `subprocess-remove!' removes a property from a
  subprocess (maybe this is a bad name?).