Provide xmlbeans-2.3.0.jar for Java 6 or higher without org.w3c.dom

The problems were already reported in the following issues:

• https://issues.apache.org/jira/browse/XMLBEANS-376
• https://issues.apache.org/jira/browse/XMLBEANS-484
  (The latter one led to fix the same problem found with both issues.)

Basically, as reported in XMLBEANS-376, xmlbeans jar library makes a jar
hell problem in JBoss, WebSphere and WebLogic even with Java 1.6!
So, they fixed the issue in v2.5.1 simply by removing org/w3c/dom/**
classes.