Saxon

A few problems with this extension function.

• It has the same bug #6029 as fn:items-at() (which reused the same code) - the results are incorrect if the second argument is an integer range such as 4 to 6.
• I can't find any test cases
• The documentation lists a number of examples in which an argument to the function uses the syntax "M by S to N" which has never been fully implemented, tested, or documented, and which is about to be withdrawn on the grounds that it's no longer being actively proposed for XPath 4.0