title: JAXB doesn't annotate with XmlRootElement
body: <p>When I generate code from the following schema, two classes are created, <code>A</code> and <code>B</code>. But, these two classes are not annotated by <code>@XmlRootElement</code>, so I get an error when I try to marshal an instance of B.</p>
  
  <p>I've looked on the web, I tried the solution using custom bindings (<code>&lt;xjc: simple/&gt;</code>) but it doesn't work. It seems that an element of type B must be defined in the schema in order for this solution to work.</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;schema xmlns:ns="com:mycomp:service" xmlns="http://www.w3.org/2001/XMLSchema"
      targetNamespace="com:mycomp:service"
      elementFormDefault="qualified" xml:lang="EN"&gt;
      &lt;complexType name="A" abstract="true"&gt;
          &lt;sequence&gt;
              &lt;element name="a1" type="string" /&gt;
          &lt;element name="a2" type="string" /&gt;
          &lt;/sequence&gt;
      &lt;/complexType&gt;
      &lt;complexType name="B"&gt;
          &lt;complexContent&gt;
              &lt;extension base="ns:A"&gt;
              &lt;sequence&gt;
                  &lt;element name="b1" type="string" /&gt;
              &lt;/sequence&gt;
          &lt;/extension&gt;
          &lt;/complexContent&gt;
      &lt;/complexType&gt;
  &lt;/schema&gt;
  </code></pre>
  
  <p>Thanks</p>