Beginning with TWS Version 939, possible values for the HALTED tick type are:
0 = Not halted
1 = General halt (trading halt is imposed for purely regulatory reasons)
with/without volatility halt.
2 = Volatility only halt (trading halt is imposed by the exchange to protect
against extreme volatility).
类似涨跌停吧，是为了保护投资者，幅度过大时候暂停交易。
这个在股市还好，在期货市场，有些品种一连四五个涨停板，逃都没法逃，
100万进去，最后倒贴broker 500万。
