message: Explicitly delete copy ctor of UbfsLinearQueue
  The copy assignment is also explicitly deleted.
  Move operators will be implicitly deleted.
diff: @@ -118,6 +118,9 @@ struct UbfsLinearQueue {
  omp_destroy_lock(&write_lock);
  }
  + UbfsLinearQueue(UbfsLinearQueue &other) = delete;
  + UbfsLinearQueue &operator=(const UbfsLinearQueue &other) = delete;
  +
  /**
  * Copies a chunk of nodes back into the work queue,
  * in a thread-safe manner.
  