message: Fix build on GCC 4.8
diff: @@ -296,6 +296,8 @@ bool engine::run(bool colorize,
  || (defined(__clang__) && !defined(_LIBCPP_VERSION))
  // regex implementation is broken prior to 4.9
  using strvec = std::vector<std::string>;
  + using whitelist_type = strvec;
  + using blacklist_type = strvec;
  auto from_psv = [](const std::string& psv) -> strvec {
  // psv == pipe-separated-values
  strvec result;
  @@ -318,6 +320,8 @@ bool engine::run(bool colorize,
  || std::binary_search(whitelist.begin(), whitelist.end(), x));
  };
  # else
  + using whitelist_type = std::regex;
  + using blacklist_type = std::regex;
  std::regex suites{suites_str};
  std::regex tests{tests_str};
  std::regex not_suites;
  @@ -335,8 +339,8 @@ bool engine::run(bool colorize,
  && !std::regex_search(x, blacklist);
  };
  # endif
  - auto test_enabled = [&](const std::regex& whitelist,
  - const std::regex& blacklist,
  + auto test_enabled = [&](const whitelist_type& whitelist,
  + const blacklist_type& blacklist,
  const test& x) {
  // Disabled tests run iff explicitly requested by the user, i.e.,
  // tests_str is not the ".*" catch-all default.
  