Improve OSGi test runner in Ant

 - Include pack/lib/*.jar in the uptodatecheck
   - (Hopefully that saves the next guy a few hours)
 - Switch the the XML formatter (I couldn't find output from the other one)
   and mention the output directory.
Another take at getting runtime reflection off the runway.

  - Change the assertion in enter to just return the existing symbol
  - Handle null classloader as seems to show up for classOf[Object].getClassloader
    in OSGi tests.
  - Remove special handling of AnnotationDefaultAttr; it isn't needed with the other changes.