Add the following members to cuda::deferred_future:   * get_ref()   * then_and_leave_valid()   * bulk_then()   * bulk_then_and_leave_valid()
Add the following members to cuda::deferred_future:
  * get_ref()
  * then_and_leave_valid()
  * bulk_then()
  * bulk_then_and_leave_valid()

egaburov/agency,egaburov/agency