bignum: expand bytearray() use, and other fixes
bignum: expand bytearray() use, and other fixes

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