message: Work around GCC 4.8 bug for disallow
diff: @@ -413,8 +413,10 @@ public:
  template <class... Us>
  void with(Us&&... xs) {
  + // TODO: replace this workaround with make_tuple() when dropping support
  + // for GCC 4.8.
  + std::tuple<typename std::decay<Us>::type...> tmp{std::forward<Us>(xs)...};
  // TODO: move tmp into lambda when switching to C++14
  - auto tmp = std::make_tuple(std::forward<Us>(xs)...);
  peek_ = [=] {
  using namespace caf::detail;
  elementwise_compare_inspector<decltype(tmp)> inspector{tmp};
  @@ -491,8 +493,10 @@ public:
  template <class... Us>
  void with(Us&&... xs) {
  + // TODO: replace this workaround with make_tuple() when dropping support
  + // for GCC 4.8.
  + std::tuple<typename std::decay<Us>::type...> tmp{std::forward<Us>(xs)...};
  // TODO: move tmp into lambda when switching to C++14
  - auto tmp = std::make_tuple(std::forward<Us>(xs)...);
  check_ = [=] {
  auto ptr = next_mailbox_element(dest_);
  if (ptr == nullptr)
  