OPENJPA-2325: MappedSuperClass without an @Id causes wrong identity type for the inherited types - back-ported to 2.1.x Pinaki Poddar's commit to trunk.

git-svn-id: https://svn.apache.org/repos/asf/openjpa/branches/2.1.x@1469949 13f79535-47bb-0310-9956-ffa450edef68