Coercion from element-with-attribute-and-text only works for `String` not other scalar types

[cowtowncoder]

Handling of text (String) valued properties works for content like:

<Root>
   <stringValue attribute="xyz">value</stringValue>
</Root>

to type like

public class Root {
   public String value;
}

(after fixes like #390)

but same is not true for other scalar types; as an example, int type fails.
This because there is special XmlStringDeserializer that handles details of handling special cases.

But it would make sense to make this work at least for int and long -- and others in future, too.