txscript/reference_test: Convert sighash calc test

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.

Backport of 06f769e

txscript/reference_test.go

@@ -836,6 +836,7 @@ func TestCalcSignatureHash(t *testing.T) {
 			err)
 	}
 
+	const scriptVersion = 0
 	for i, test := range tests {
 		if i == 0 {
 			// Skip first line -- contains comments only.
@@ -855,15 +856,15 @@ func TestCalcSignatureHash(t *testing.T) {
 		}
 
 		subScript, _ := hex.DecodeString(test[1].(string))
-		parsedScript, err := parseScript(subScript)
+		err = checkScriptParses(scriptVersion, subScript)
 		if err != nil {
 			t.Errorf("TestCalcSignatureHash failed test #%d: "+
 				"Failed to parse sub-script: %v", i, err)
 			continue
 		}
 
 		hashType := SigHashType(testVecF64ToUint32(test[3].(float64)))
-		hash, err := calcSignatureHash(parsedScript, hashType, &tx,
+		hash, err := CalcSignatureHash(subScript, hashType, &tx,
 			int(test[2].(float64)))
 		if err != nil {
 			t.Errorf("TestCalcSignatureHash failed test #%d: "+