title: SerializationPolicy error when performing RPC from within GWT application
body: <p>I'm getting the following exception:</p>
  
  <blockquote>
    <p>com.google.gwt.user.client.rpc.SerializationException: Type 'java.lang.Long' was not included in the set of types which can be serialized by this SerializationPolicy or its Class object could not be loaded. For security purposes, this type will not be serialized</p>
  </blockquote>
  
  <p>using GWT 2.1 and the built in Jetty server. According to the docs, this type is definitely serializable... How can I include it in the SerializationPolicy?</p>