Added Constantinople difficulty bomb delay
Added Constantinople difficulty bomb delay

ethereumjs/ethereumjs-vm,ethereumjs/ethereumjs-vm,ethereumjs/ethereumjs-vm,ethereumjs/ethereumjs-vm,ethereum/ethereumjs-vm,ethereumjs/ethereumjs-vm,ethereumjs/ethereumjs-block,ethereumjs/ethereumjs-block,ethereumjs/ethereumjs-block