1. Block gas limit variation change from range mode to target mode.
Before upgrade, the default block gas limit range from 15M to 40M, only when each block is full it will reach the max value 40M, only when each block is full it will reach the max value 40M,
1. 阻止从范围模式到目标模式的气体限制变化。
升级前，默认区块gas限制范围为15M到40M，每个区块满了才达到最大值40M，每个区块满了才达到最大值40M，