Add negative tests for cref() and rvalues.

test/ref_rv_fail5.cpp

@@ -0,0 +1,27 @@
+//
+// Test that a const rvalue can't be passed to cref()
+//
+// Copyright 2014 Agustin Berge
+// Copyright 2014 Peter Dimov
+//
+// Distributed under the Boost Software License, Version 1.0.
+// See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt
+//
+
+#include <boost/ref.hpp>
+
+#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
+
+struct X {};
+
+X const crv() { return X(); }
+
+int main()
+{
+    boost::reference_wrapper<X const> r = boost::cref( crv() ); // must fail
+}
+
+#else
+#  error To fail, this test requires rvalue references.
+#endif