message: Simplify Windows platform check
  The official way to detect both Win32 and Win64 is with `_WIN32`.
  Check for only Win64 with `_WIN64`.
diff: @@ -241,7 +241,7 @@ void MainMenuState::btnHelpClicked()
  {
  if (mFileIoDialog.visible()) { return; }
  -#if defined(WINDOWS) || defined(WIN32)
  +#if defined(_WIN32)
  system("start https://wiki.outpost2.net/doku.php?id=outposthd:how_to_play");
  #elif defined(__APPLE__)
  system("open https://wiki.outpost2.net/doku.php?id=outposthd:how_to_play");
  