$OpenBSD: patch-boost_type_traits_is_convertible_hpp,v 1.1 2017/05/30 18:00:53 zhuk Exp $
Unbreak compilation with libc++ in non-c++11 mode.
The v1/__config uses #define decltype(__x) __decltype(__x),
which doesn't work for the decltype(x,y) case.

Index: boost/type_traits/is_convertible.hpp
--- boost/type_traits/is_convertible.hpp.orig
+++ boost/type_traits/is_convertible.hpp
@@ -83,7 +83,7 @@ namespace detail {
       static void test_aux(To1);
 
       template<typename From1, typename To1>
-      static decltype(test_aux<To1>(boost::declval<From1>()), one()) test(int);
+      static __decltype(test_aux<To1>(boost::declval<From1>()), one()) test(int);
 
       template<typename, typename>
       static two test(...);
