Add compile-fail test for const boost::Wrapper

test/swap/const_wrapper_fail.cpp

@@ -0,0 +1,28 @@
+// Copyright 2018 Andrzej Krzemieński
+// Copyright 2018 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+
+#include <boost/core/swap.hpp>
+
+namespace boost
+{
+  
+template<class T> struct Wrapper
+{
+    T value;
+};
+
+template<class T> inline void swap( Wrapper<T> & w, Wrapper<T> & v )
+{
+    boost::swap( w, v );
+}
+  
+} // namespace boost
+ 
+int main()
+{
+    boost::Wrapper<int> const w = { 2 };
+    boost::Wrapper<int> const v = { 3 };
+
+    swap( w, v );
+}