gstring.go
func Sprintm(format string, args map[string]interface{}) string {
	f, a := gformat(format, args)
	return fmt.Sprintf(f, a...)
}
func Sprintm(format string, args map[string]interface{}) string {
	f, a := gformat(format, args)
	return fmt.Sprintf(f, a...)
}
// Sprintf returns formatted string.
// This is same as fmt.Sprintf, but uses gstring formatting.