Underlying SQLException information is lost when DuplicateIdentityException is created

when processing SQLException in SQLStatementCreate, code tries to detect duplicate identity exception - if such is detected, new DuplicateIdentityException is created without saving original SQLException (which provides way more information about the cause of the exception) as nested one.

the patch is really trivial:

original org.exolab.castor.jdo.engine.SQLStatementCreate code:

line 326: throw new DuplicateIdentityException(Messages.format("persist.duplicateIdentity", _type, identity));

corrected code:

line 326: throw new DuplicateIdentityException(Messages.format("persist.duplicateIdentity", _type, identity), except);