Backport Castor to Java 1.3 compatibility: Exceptions do not support claus

various places (28 errors):

Exception and RuntimeException do not support cause (e.g. constructor Exception(String, Throwable) is missing). To fix that while still being able to pass root cause we need to subclass some exceptions (e.g. SAXException).

Wrt the exceptions, I am not really sure, but I somehow wouldn't mind providing new exception types. It would be a change in contract, but that to me seems to be the smaller problem for 1.3 users ... .