Make id() function XPath 2.0 compatible

Original post from MichaelKay:

Date: Mon, 23 Apr 2007 23:49:32 +0200
To: www-forms-editor@w3.org
Subject: 7.11.4
From: "Michael Kay" <mike@saxonica.com>
Cc: "'XQuery'" <w3c-xml-query-wg@w3.org>, "'XSL WG'" <w3c-xsl-wg@w3.org>

    N. The two-argument id() function poses particular problems because
    its semantics are very similar but not identical to the
    two-argument id() function in XPath 2.0

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