In preparation for the potential Taproot soft fork, libconsensus should be updated to support verifying Taproot scripts.

There are two changes I see as necessary:

- Add a VERIFY_TAPROOT flag
- Change the API to support passing in spent outputs (bitcoinconsensus_verify_script_with_spent_outputs?)
{
    return (flags & ~(bitcoinconsensus_SCRIPT_FLAGS_VERIFY_ALL)) == 0;
}
static int verify_script(const unsigned char *scriptPubKey, unsigned int scriptPubKeyLen, CAmount amount,
                                    const unsigned char *txTo        , unsigned int txToLen,
                                    unsigned int nIn, unsigned int flags, bitcoinconsensus_error* err)
{
    if (!verify_flags(flags)) {
        return set_error(err, bitcoinconsensus_ERR_INVALID_FLAGS);
    }
    try {
        TxInputStream stream(PROTOCOL_VERSION, txTo, txToLen);
        CTransaction tx(deserialize, stream);
        if (nIn >= tx.vin.size())
            return set_error(err, bitcoinconsensus_ERR_TX_INDEX);
        if (GetSerializeSize(tx, PROTOCOL_VERSION) != txToLen)
            return set_error(err, bitcoinconsensus_ERR_TX_SIZE_MISMATCH);
        
        set_error(err, bitcoinconsensus_ERR_OK);
        PrecomputedTransactionData txdata(tx);
        return VerifyScript(tx.vin[nIn].scriptSig, CScript(scriptPubKey, scriptPubKey + scriptPubKeyLen), &tx.vin[nIn].scriptWitness, flags, TransactionSignatureChecker(&tx, nIn, amount, txdata, MissingDataBehavior::FAIL), nullptr);
    } catch (const std::exception&) {
        return set_error(err, bitcoinconsensus_ERR_TX_DESERIALIZE); 
    }
}
int bitcoinconsensus_verify_script_with_amount(const unsigned char *scriptPubKey, unsigned int scriptPubKeyLen, int64_t amount,