make validateSlashingTx private as it should not be part of the public api, the validation of slashing tx only have point in context of validation of funding/slashing transactions pair
add check for slashing and funding transaction - blockchain.CheckTransactionSanity which check transactions against BTC rules which are relevant to overlfows and transactions limits.
validateSlashingTxprivate as it should not be part of the public api, the validation of slashing tx only have point in context of validation of funding/slashing transactions pairblockchain.CheckTransactionSanitywhich check transactions against BTC rules which are relevant to overlfows and transactions limits.