Update tengo vendor and load the stdlib. Fixes #789 (#792)

vendor/github.com/d5/tengo/objects/builtins.go

@@ -2,19 +2,7 @@ package objects
 
 // Builtins contains all default builtin functions.
 // Use GetBuiltinFunctions instead of accessing Builtins directly.
-var Builtins = []BuiltinFunction{
-	{
-		Name:  "print",
-		Value: builtinPrint,
-	},
-	{
-		Name:  "printf",
-		Value: builtinPrintf,
-	},
-	{
-		Name:  "sprintf",
-		Value: builtinSprintf,
-	},
+var Builtins = []*BuiltinFunction{
 	{
 		Name:  "len",
 		Value: builtinLen,
@@ -95,6 +83,10 @@ var Builtins = []BuiltinFunction{
 		Name:  "is_immutable_map",
 		Value: builtinIsImmutableMap,
 	},
+	{
+		Name:  "is_iterable",
+		Value: builtinIsIterable,
+	},
 	{
 		Name:  "is_time",
 		Value: builtinIsTime,
@@ -115,50 +107,8 @@ var Builtins = []BuiltinFunction{
 		Name:  "is_callable",
 		Value: builtinIsCallable,
 	},
-	{
-		Name:  "to_json",
-		Value: builtinToJSON,
-	},
-	{
-		Name:  "from_json",
-		Value: builtinFromJSON,
-	},
 	{
 		Name:  "type_name",
 		Value: builtinTypeName,
 	},
 }
-
-// AllBuiltinFunctionNames returns a list of all default builtin function names.
-func AllBuiltinFunctionNames() []string {
-	var names []string
-	for _, bf := range Builtins {
-		names = append(names, bf.Name)
-	}
-	return names
-}
-
-// GetBuiltinFunctions returns a slice of builtin function objects.
-// GetBuiltinFunctions removes the duplicate names, and, the returned builtin functions
-// are not guaranteed to be in the same order as names.
-func GetBuiltinFunctions(names ...string) []*BuiltinFunction {
-	include := make(map[string]bool)
-	for _, name := range names {
-		include[name] = true
-	}
-
-	var builtinFuncs []*BuiltinFunction
-	for _, bf := range Builtins {
-		if include[bf.Name] {
-			bf := bf
-			builtinFuncs = append(builtinFuncs, &bf)
-		}
-	}
-
-	return builtinFuncs
-}
-
-// GetAllBuiltinFunctions returns all builtin functions.
-func GetAllBuiltinFunctions() []*BuiltinFunction {
-	return GetBuiltinFunctions(AllBuiltinFunctionNames()...)
-}