message: Fix build on Clang and MSVC
diff: @@ -106,11 +106,20 @@ public:
  // nop
  }
  +#ifdef CAF_GCC
  constexpr string_view(const char* cstr) noexcept
  : data_(cstr),
  size_(strlen(cstr)) {
  // nop
  }
  +#else
  + template <size_t N>
  + constexpr string_view(const char (&cstr)[N]) noexcept
  + : data_(cstr),
  + size_(N - 1) {
  + // nop
  + }
  +#endif
  constexpr string_view(const string_view&) noexcept = default;
  