docs: public final void enqueue(Object obj)
    {
  //    if (tc.isEntryEnabled())
  //      SibTr.entry(tc, "enqueue", obj);
      // m_array has at least one position in it that is free.
      m_array[m_tail++] = obj;
      if (m_tail == m_array.length)
        m_tail = 0;
      if (m_head == m_tail)
        expand_array();
  //    if (tc.isEntryEnabled())
  //      SibTr.exit(tc, "enqueue");
    }