add checkpoint at block 20580 and remove old version node
add checkpoint at block 20580 and remove old version node

hexxcointakeover/hexxcoin,zcoinofficial/zcoin,zcoinofficial/zcoin,real-or-random/zcoin,hexxcointakeover/hexxcoin,SmartCash/smartcash,psolstice/zcoin,zcoinofficial/zcoin,hexxcointakeover/hexxcoin,zcoinofficial/zcoin,zcoinofficial/zcoin,psolstice/zcoin,hexxcointakeover/hexxcoin,zcoinofficial/zcoin,psolstice/zcoin,aizensou/zcoin,hexxcointakeover/hexxcoin,SmartCash/smartcash,aizensou/zcoin,zcoinofficial/zcoin,zcoinofficial/zcoin,hexxcointakeover/hexxcoin,real-or-random/zcoin,SmartCash/smartcash,hexxcointakeover/hexxcoin,real-or-random/zcoin,SmartCash/smartcash,aizensou/zcoin,aizensou/zcoin,aizensou/zcoin,SmartCash/smartcash,zcoinofficial/zcoin,psolstice/zcoin,psolstice/zcoin,real-or-random/zcoin,hexxcointakeover/hexxcoin,hexxcointakeover/hexxcoin,SmartCash/smartcash,zcoinofficial/zcoin,psolstice/zcoin,real-or-random/zcoin,hexxcointakeover/hexxcoin