Unmarshal returns an error with v0.5.0

[jerome-laforge]

With v0.5.0, xml.Unmarshal returns an error:

	r := soap.SOAPEnvelope{
		Body: soap.SOAPBody{
			Content: &InfoRequest{},
		},
	}
	if err := xml.Unmarshal(buf, &r); err != nil {
		return nil, err
	}

xml.Unmarshal returns expected element type <soap:Envelope> but have <Envelope> with Go 1.16