Add stack trace Wrap method

[reindert-vetter]

func (f *fundamental) Wrap(message string, args ...interface{}) *withMessage {
	return WithMessage(f, message, args...)
}

to

func (f *fundamental) Wrap(message string, args ...interface{}) *withMessage {
// if stack already exists:
        return WithMessage(f, message, args...)
// else:
	return Wrap(f, message, args...)
}

see also other 'Wrap' methods