wally: Build wally transactions in parallel with the old ones

Signed-off-by: Christian Decker <decker.christian@gmail.com>

bitcoin/signature.c

@@ -109,12 +109,21 @@ void sign_tx_input(const struct bitcoin_tx *tx,
 		   enum sighash_type sighash_type,
 		   struct bitcoin_signature *sig)
 {
-	struct sha256_double hash;
+	struct sha256_double hash, whash;
+	int flags = witness_script != NULL ? WALLY_TX_FLAG_USE_WITNESS : 0;
+	const u8 *script = witness_script ? witness_script : subscript;
 
 	assert(sighash_type_valid(sighash_type));
 	sig->sighash_type = sighash_type;
+	wally_tx_get_btc_signature_hash(
+	    tx->wtx, in, script, tal_bytelen(script),
+	    tx->input[in].amount->satoshis /* Raw: low-level helper */,
+	    sighash_type, flags, whash.sha.u.u8, sizeof(whash));
 	sha256_tx_one_input(tx, in, subscript, witness_script,
 			    sighash_type, &hash);
+
+	assert(memeq(&hash, sizeof(hash), &whash, sizeof(whash)));
+
 	dump_tx("Signing", tx, in, subscript, key, &hash);
 	sign_hash(privkey, &hash, &sig->s);
 }