[security-services] Approved addition to core: Multi-Valued Attributes

The committee approved the addition of explicit support for multi-valued
attributes with this proposal. It also corrects the text to reflect the
earlier change of the element's type from "AttributeValueType" to
"anyType", which will appear in the forthcoming revision of the
document.

In core-25, section 2.4.5.1, change the schema on line 807:
	<element ref="saml:AttributeValue"/>
to:
	<element ref="saml:AttributeValue" maxOccurs="unbounded"/>

In section 2.4.5.1.1, change the first paragraph (lines 813-815) to:

The <AttributeValue> element(s) supply one or more values of the
specified attribute. It is of the simple type "anyType", which allows
any well-formed XML to appear as the content of the element.

-- Scott