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

vendor/github.com/d5/tengo/stdlib/stdlib.go

@@ -0,0 +1,34 @@
+package stdlib
+
+//go:generate go run gensrcmods.go
+
+import "github.com/d5/tengo/objects"
+
+// AllModuleNames returns a list of all default module names.
+func AllModuleNames() []string {
+	var names []string
+	for name := range BuiltinModules {
+		names = append(names, name)
+	}
+	for name := range SourceModules {
+		names = append(names, name)
+	}
+	return names
+}
+
+// GetModuleMap returns the module map that includes all modules
+// for the given module names.
+func GetModuleMap(names ...string) *objects.ModuleMap {
+	modules := objects.NewModuleMap()
+
+	for _, name := range names {
+		if mod := BuiltinModules[name]; mod != nil {
+			modules.AddBuiltinModule(name, mod)
+		}
+		if mod := SourceModules[name]; mod != "" {
+			modules.AddSourceModule(name, []byte(mod))
+		}
+	}
+
+	return modules
+}