C++: add test for anonymous with __attribute__

Change-Id: I1938ed1bf45523ec62f35bc3324f6553c0dafe22
Sanity-Review: Qt Sanity Bot <qt_sanitybot@qt-project.org>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>

tests/auto/cplusplus/ast/tst_ast.cpp

@@ -1779,6 +1779,7 @@ void tst_AST::unnamed_class_data()
     typedef QByteArray _;
     QTest::newRow("unnamed-only") << _("class {};");
     QTest::newRow("unnamed-derived") << _("class : B {};");
+    QTest::newRow("unnamed-__attribute__") << _("class __attribute__((aligned(8))){};");
 }
 
 void tst_AST::initTestCase()