message: Remove dead code, fix ambiguous function signature
diff: #include "caf/actor_control_block.hpp"
  #include "caf/check_typed_input.hpp"
  #include "caf/detail/profiled_send.hpp"
  +#include "caf/detail/type_traits.hpp"
  #include "caf/duration.hpp"
  #include "caf/fwd.hpp"
  #include "caf/message.hpp"
  @@ -75,23 +76,10 @@ public:
  }
  /// Sends `{xs...}` as an asynchronous message to `dest` with priority `mp`.
  - template <message_priority P = message_priority::normal, class... Ts>
  - void send(const strong_actor_ptr& dest, Ts&&... xs) {
  - using detail::type_list;
  - static_assert(sizeof...(Ts) > 0, "no message to send");
  - static_assert(!statically_typed<Subtype>(),
  - "statically typed actors can only send() to other "
  - "statically typed actors; use anon_send() or request() when "
  - "communicating with dynamically typed actors");
  - auto self = dptr();
  - detail::profiled_send(self, dest, self->ctrl(), make_message_id(P), {},
  - std::forward<Ts>(xs)...);
  - }
  -
  - /// Sends `{xs...}` as an asynchronous message to `dest` with priority `mp`.
  - template <message_priority P = message_priority::normal, class Dest = actor,
  + template <message_priority P = message_priority::normal, class Dest,
  class... Ts>
  - void send(const Dest& dest, Ts&&... xs) {
  + detail::enable_if_t<!std::is_same<group, Dest>::value> send(const Dest& dest,
  + Ts&&... xs) {
  static_assert(sizeof...(Ts) > 0, "no message to send");
  detail::type_list<detail::strip_and_convert_t<Ts>...> args_token;
  type_check(dest, args_token);
  