message: Fix to_string unit test on Raspbian, close
diff: @@ -28,7 +28,8 @@ using namespace std;
  using namespace caf;
  CAF_TEST(buffer) {
  - std::vector<char> buf;
  + // Use `signed char` explicitly to make sure all compilers agree.
  + std::vector<signed char> buf;
  CAF_CHECK_EQUAL(deep_to_string(buf), "[]");
  CAF_CHECK_EQUAL(deep_to_string(meta::hex_formatted(), buf), "00");
  buf.push_back(-1);
  