txscript: Convert sighash calc tests.

This converts the tests for calculating signature hashes to use the
exported function which handles the raw script versus the now deprecated
variant requiring parsed opcodes.

txscript/reference_test.go

@@ -1,5 +1,5 @@
 // Copyright (c) 2013-2017 The btcsuite developers
-// Copyright (c) 2015-2018 The Decred developers
+// Copyright (c) 2015-2019 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -828,6 +828,7 @@ func TestCalcSignatureHashReference(t *testing.T) {
 		t.Fatalf("TestCalcSignatureHash couldn't Unmarshal: %v\n", err)
 	}
 
+	const scriptVersion = 0
 	for i, test := range tests {
 		// Skip comment lines.
 		if len(test) == 1 {
@@ -869,7 +870,7 @@ func TestCalcSignatureHashReference(t *testing.T) {
 				err)
 			continue
 		}
-		parsedScript, err := parseScript(subScript)
+		err = checkScriptParses(scriptVersion, subScript)
 		if err != nil {
 			t.Errorf("Test #%d: unable to parse script: %v", i, err)
 			continue
@@ -915,7 +916,7 @@ func TestCalcSignatureHashReference(t *testing.T) {
 		}
 
 		// Calculate the signature hash and verify expected result.
-		hash, err := calcSignatureHash(parsedScript, hashType, &tx,
+		hash, err := CalcSignatureHash(subScript, hashType, &tx,
 			int(inputIdxF64), nil)
 		if (err == nil) != (expectedErr == nil) ||
 			expectedErr != nil && !IsErrorCode(err, *expectedErr) {