Apply predetermined block for testnet fork
Apply predetermined block for testnet fork

PR #589 caused a condition for testnet difficulty to not match at
a couple of cases pre block 145k leading to issues with -reindex.

This makes the testnet fork hard at block 157500, while retaining
every case before that block.

Domer85/dogecoin,langerhans/dogecoin,koharjidan/dogecoin,haisee/dogecoin,brishtiteveja/sherlockcoin,brishtiteveja/sherlockcoin,brishtiteveja/sherlockcoin,langerhans/dogecoin,coinwarp/dogecoin,jarymoth/dogecoin,marklai9999/Taiwancoin,coinkeeper/2015-06-22_18-37_dogecoin,langerhans/dogecoin,Exceltior/dogecoin,jarymoth/dogecoin,koharjidan/dogecoin,Exceltior/dogecoin,koharjidan/dogecoin,marklai9999/Taiwancoin,jarymoth/dogecoin,Domer85/dogecoin,coinwarp/dogecoin,langerhans/dogecoin,haisee/dogecoin,langerhans/dogecoin,Domer85/dogecoin,haisee/dogecoin,jarymoth/dogecoin,brishtiteveja/sherlockcoin,coinwarp/dogecoin,koharjidan/dogecoin,langerhans/dogecoin,coinkeeper/2015-06-22_18-37_dogecoin,Domer85/dogecoin,coinwarp/dogecoin,coinwarp/dogecoin,brishtiteveja/sherlockcoin,koharjidan/dogecoin,koharjidan/dogecoin,Exceltior/dogecoin,coinkeeper/2015-06-22_18-37_dogecoin,marklai9999/Taiwancoin,coinkeeper/2015-06-22_18-37_dogecoin,coinkeeper/2015-06-22_18-37_dogecoin,Exceltior/dogecoin,haisee/dogecoin,Exceltior/dogecoin,jarymoth/dogecoin,marklai9999/Taiwancoin,haisee/dogecoin