portable way to resolve the CategoryAttribute ambiguity.
* XamlObjectReaderTest.cs, XamlObjectWriterTest.cs: Likewise.
* XamlTypeTest.cs, XamlXmlReaderTest.cs, XamlXmlWriterTest.cs: Likewise.
+ * XamlDirectiveTest.cs: Likewise.
2010-05-17 Atsushi Enomoto <atsushi@ximian.com>