add_attribute_int
Description:
Adds a new attribute with an integer value to the current element.
 Use null ns_href, to use the default namespace, otherwise either previously added namespace with the same href from 
      e_xml_document_add_namespaces is picked, or a new namespace with generated prefix is added.
Parameters:
| this | an XmlDocument | 
| ns_href | optional namespace href for the new attribute, or  | 
| name | name of the attribute | 
| value | integer value of the attribute |