Change p:system-property to return untyped atomic

Folks,

I propose that we change the signature of p:system-property() so that
it returns an untyped atomic in an XPath 2.0 processor.

Otherwise, "p:system-property('p:version') > 1.0" returns a type error
(you can't compare a string to a decimal).

                                        Be seeing you,
                                          norm

-- 
Norman Walsh <ndw@nwalsh.com> | A language is a dialect that has an
http://nwalsh.com/            | army and a navy.--Max Weinreich