message: core(trace): lazy quering for OPENCV_TRACE_LOCATION
  fixes proper initialization of non-trivial variable
diff: @@ -82,7 +82,12 @@ static bool getParameterTraceEnable()
  static int param_maxRegionDepthOpenCV = (int)utils::getConfigurationParameterSizeT("OPENCV_TRACE_DEPTH_OPENCV", 1);
  static int param_maxRegionChildrenOpenCV = (int)utils::getConfigurationParameterSizeT("OPENCV_TRACE_MAX_CHILDREN_OPENCV", 1000);
  static int param_maxRegionChildren = (int)utils::getConfigurationParameterSizeT("OPENCV_TRACE_MAX_CHILDREN", 10000);
  +
  +static const cv::String& getParameterTraceLocation()
  +{
  static cv::String param_traceLocation = utils::getConfigurationParameterString("OPENCV_TRACE_LOCATION", "OpenCVTrace");
  + return param_traceLocation;
  +}
  #ifdef HAVE_OPENCL
  static bool param_synchronizeOpenCL = utils::getConfigurationParameterBool("OPENCV_TRACE_SYNC_OPENCL", false);
  @@ -813,7 +818,7 @@ TraceStorage* TraceManagerThreadLocal::getStorage() const
  TraceStorage* global = getTraceManager().trace_storage.get();
  if (global)
  {
  - const std::string filepath = cv::format("%s-%03d.txt", param_traceLocation.c_str(), threadID).c_str();
  + const std::string filepath = cv::format("%s-%03d.txt", getParameterTraceLocation().c_str(), threadID).c_str();
  TraceMessage msg;
  const char* pos = strrchr(filepath.c_str(), '/'); // extract filename
  #ifdef _WIN32
  @@ -848,7 +853,7 @@ TraceManager::TraceManager()
  activated = getParameterTraceEnable();
  if (activated)
  - trace_storage.reset(new SyncTraceStorage(std::string(param_traceLocation) + ".txt"));
  + trace_storage.reset(new SyncTraceStorage(std::string(getParameterTraceLocation()) + ".txt"));
  #ifdef OPENCV_WITH_ITT
  if (isITTEnabled())
  