title: XML remove nil attribute
body: <p>I am doing some XmlOverrides and setting properties to nullable (F1 in this case). I would want to delete nil="true" and the namespace around this attribute, but I can't remove it with any method I've tried.  </p>
  
  <pre><code>Nested n = new Nested();
  n.Nest = "2";
  n.F1 = null;
  
  XmlAttributeOverrides overrides = new XmlAttributeOverrides();
  
  XmlAttributes att = new XmlAttributes();
  XmlElementAttribute el = new XmlElementAttribute("F1");
  el.IsNullable = true;
  att.XmlElements.Add(el);
  overrides.Add(typeof(Nested), "F1", att);
  
  XmlSerializer xs = new XmlSerializer(typeof(Nested), overrides);
  
  var faultDocument = new XmlDocument();
  var nav = faultDocument.CreateNavigator();
  var ns = new XmlSerializerNamespaces();
  ns.Add("", "");
  
  using (var writer = nav.AppendChild())
  {
      xs.Serialize(writer, n, ns);
  }
  </code></pre>
  
  <p>XML I get is like this:</p>
  
  <pre><code>&lt;Nested&gt;
      &lt;F1 p2:nil="true" xmlns:p2="http://www.w3.org/2001/XMLSchema-instance"/&gt;
      &lt;Nest&gt;2&lt;/Nest&gt;
  &lt;/Nested&gt;
  </code></pre>
  
  <p>But I would want that F1 element be empty, without nil and xmlns</p>
  
  <pre><code>&lt;Nested&gt;
      &lt;F1/&gt;
      &lt;Nest&gt;2&lt;/Nest&gt;
  &lt;/Nested&gt;
  </code></pre>