Update throw_from_library_test.cpp

test/lib4_throw.cpp

@@ -0,0 +1,14 @@
+// Copyright 2018 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 "lib4_throw.hpp"
+#include <boost/throw_exception.hpp>
+
+void lib4::f()
+{
+    boost::throw_exception( lib4::exception() );
+}