message: QGC Mission Importer: Use `WINDOWS` flag instead of WIN32
  Used `WINDOWS` macro for consistency.
diff: #include "log.h"
  // To locate QGroundControl plan file during Unit test.
  -#if defined(WIN32) || defined(_WIN32) || defined(__WIN32)
  +#ifdef WINDOWS
  const std::string SLASH = "\\";
  #else
  const std::string SLASH = "/";
  