Saxon

Some low-level utility methods in Saxon throw an UncheckedXPathException; this is so that they can implement the increasing number of JDK interfaces (Iterator being a classical example) that don't allow checked exceptions.

This puts the onus on the calling code to check for UncheckedXPathException and convert it to a (checked) XPathException.

We have a crash in test case map:for-each-405 caused by the fact that method FunctionSequenceCoercer.simplify() fails to make this check; while we're about it we'll search for other methods that call SequenceTool.toGroundedValue() and fail to check for the exception.