message: Default the default constructor of overloaded
  Avoids some nasty interaction between defaulted and inherited default constructors that manifests with g++-4.9 in utility.variant and view.transform.
diff: @@ -450,13 +450,7 @@ namespace ranges
  using base_t::first;
  using base_t::second;
  public:
  - CONCEPT_REQUIRES(meta::and_<
  - DefaultConstructible<First>, DefaultConstructible<Rest>...>())
  - constexpr overloaded()
  - noexcept(meta::strict_and<
  - std::is_nothrow_default_constructible<First>,
  - std::is_nothrow_default_constructible<Rest>...>::value)
  - {}
  + overloaded() = default;
  constexpr overloaded(First first, Rest... rest)
  : overloaded::compressed_pair{
  detail::move(first),
  