When a warning occurs at (un)marshalling time, leave the 'source' argument to null for now.
The previous attempt to provide a non-null value added more complexity than initially though,
and we had no consistent value. In a future version, the Marshaller or Unmarshaller instance
may be a more appropriate argument than what we had - but for now we wait to see a need for that.


git-svn-id: https://svn.apache.org/repos/asf/sis/branches/JDK7@1551107 13f79535-47bb-0310-9956-ffa450edef68