Build failure under JDK6

[Alex Grönholm]

I was unable to compile OpenEJB on JDK6 due to missing methods in 
org.apache.openejb.persistence.PersistenceBootstrap.NullDataSource. I 
opened a JIRA issue (OPENEJB-952) and attached a patch that adds the 
required methods. The build still fails due to problems elsewhere in the 
project though.