Revive old validate Tx in parallel code, faster...
Revive old validate Tx in parallel code, faster...

requested by davec, cleanup/polish in-tree.

btcsuitereleases/btcd,Roasbeef/btcd,hectorj/btcd,Stash-Crypto/btcd,FactomProject/btcd,jongillham/btcd,dajohi/btcd,mathiasrw/btcd,BitGo/prova,Cleawing/btcd,Cleawing/btcd,Dirbaio/btcd,tb00/btcd,runeaune/btcd,jrick/dcrd,soapboxsys/ombfullnode,hectorj/btcd,qchain/btcd,adiabat/btcd,CryptocurrencyCabal/htcd,adiabat/btcd,cjepson/btcd,ltcsuite/ltcd,BitGo/prova,dan-da/btcd,tb00/btcd,jrick/dcrd,jcmincke/dcrd,DanielKrawisz/btcd,cjepson/btcd,jcmincke/dcrd,jimmysong/btcd,dajohi/btcd,davecgh/btcd,toddfries/btcd,FactomProject/btcd,qchain/btcd,1d4Nf6/btcd,mathiasrw/btcd,jimmysong/btcd,aakselrod/btcd,stevenroose/btcd,davecgh/btcd,sysbot/btcd,btcsuite/btcd,Stash-Crypto/btcd,glv2/ppcd,jrick/btcd,Roasbeef/btcd,runeaune/btcd,wallclockbuilder/btcd,ppcsuite/ppcd,wallclockbuilder/btcd,ppcsuite/ppcd-old,pkothbauer/btcd,jcmincke/dcrd,Dirbaio/btcd,danoctavian/btcd,jongillham/btcd,1d4Nf6/btcd,decred/dcrd,glv2/ppcd,ppcsuite/ppcd-old,dan-da/btcd,pkothbauer/btcd,sysbot/btcd,danoctavian/btcd,jrick/btcd,btcsuite/btcd,btcsuitereleases/btcd,aakselrod/btcd,jrick/btcd,ppcsuite/ppcd,toddfries/btcd,Dirbaio/btcd,cqswxj2013/btcd,soapboxsys/ombfullnode,CryptocurrencyCabal/htcd,dajohi/btcd,decred/dcrd,DanielKrawisz/btcd,ltcsuite/ltcd,cqswxj2013/btcd,stevenroose/btcd