XQuery 3.0 implementation

Saxon 9.5 fully implements the XQuery 3.0 Candidate Recommendation of January 2013.

Forwards references to global variables are now allowed.

Added support for variables such as err:code and err:description within the catch block of try/catch.

Added support for function annotations.

Added support for the required-feature and prohibited-feature declarations.

XQuery 3.0 extensions can now co-exist with XQuery Update extensions in the same query.