message: Add clear() method to ConditionStack class
diff: @@ -290,6 +290,11 @@ private:
  public:
  bool empty() { return m_stack_size == 0; }
  bool all_true() { return m_first_false_pos == NO_FALSE; }
  + void clear()
  + {
  + m_stack_size = 0;
  + m_first_false_pos = NO_FALSE;
  + }
  void push_back(bool f)
  {
  if (m_first_false_pos == NO_FALSE && !f)
  