message: Fix up streambuf unit test
diff: @@ -48,7 +48,7 @@ CAF_TEST(signed_arraybuf) {
  auto c = ab.sgetc();
  CAF_CHECK_EQUAL(c, charbuf::traits_type::eof());
  // Reset the stream and write into it.
  - ab.setbuf(&data[0], static_cast<std::streamsize>(data.size()));
  + ab.pubsetbuf(&data[0], static_cast<std::streamsize>(data.size()));
  CAF_CHECK_EQUAL(static_cast<size_t>(ab.in_avail()), data.size());
  auto put = ab.sputn("One", 3);
  CAF_CHECK_EQUAL(put, 3);
  