Add failing test for DDC-1787.

Using joined table inheritance, when persisting multiple new entities
that are subclasses of a baseclass that has the @Version attribute set,
only the last persisted entity will have it's version set.
Fix DDC-1787.

Credit goes to Jack van Galen for fixing this issue.
Fix for JoinedSubclassPersister, multiple inserts with versioning throws
an optimistic locking exception.
Merge pull request #877 from aaronmu/DDC-1787

Hotfix for DDC-1787