Saxon extensions to the W3C XSLT/XQuery specifications

Added extension functions: saxon:parse() and saxon:serialize(). These allow conversion of a string containing well-formed XML to a tree structure, and vice-versa.

Added extension functions: saxon:string-to-unicode() and saxon:unicode-to-string(). These allow conversion between a string and a sequence of integers representing the Unicode values of the characters in the string.

Added extension functions saxon:pause-tracing() and saxon:resume-tracing().