JAXP interface (transformation, XPath, schema processing)

The usage of the three methods warning(), error(), and fatalError() in the ErrorListener class has changed. This is in line with clarifications made to the JAXP specification, and with the behavior of other products. Conditions classified in the XSLT, XQuery, or XPath specifications as errors are now notified to the fatalError() method. Conditions described in the XSLT specification as recoverable errors are notified to the error() method, provided that Saxon is capable of recovering from them. The warning() method is now used only for conditions that are not errors according to the W3C language specifications, but indicate that something might be wrong.