Saxon extensions to the W3C XSLT/XQuery specifications

The extension functions saxon:index() and saxon:find() have been changed. These functions allow creation of a user-defined index over a sequence, and fast retrieval of items from the sequence by using the index. The function saxon:index() no longer returns the sequence in question, rather it now defines an object of type {}com.saxonica.extra.IndexedSequence which can be used only as input to the saxon:find() function. The saxon:find() function now has a one-argument version which returns the sequence in question. This change has been made for robsustness: the existing design was proving excessively difficult to maintain.