Support "alert" message, CAlert and CUnsignedAlert
Support "alert" message, CAlert and CUnsignedAlert

robertsdotpm/python-bitcoinlib,daedalus/python-bitcoin_r,petertodd/tx-flood-attack,jgarzik/python-bitcoinlib,petertodd/dust-b-gone,petertodd/stealth-addresses-ref-implementation,jgarzik/pynode,daedalus/pynode