message: Make to_char_t thread-safe (win)
  This creates a local "cache" by having a thread-local static variable containing the reformatted copy of the string.
  Closes
diff: @@ -225,7 +225,7 @@ std::string trim_whitespace(const std::string &str)
  const char_t *to_char_t(const std::string &s) {
  #if defined(_WIN32) || defined(WIN32)
  - std::wstring ws;
  + static thread_local std::wstring ws;
  Poco::UnicodeConverter::toUTF16(s, ws);
  return ws.c_str();
  #else
  