message: features2d: don't use rand(), because it is not thread-safe
  Results are not stable with srand()
diff: @@ -2077,7 +2077,7 @@ void generateDescriptorSubsample(Mat& sampleList, Mat& comparisons, int nbits,
  }
  }
  - srand(1024);
  + RNG rng(1024);
  Mat_<int> comps = Mat_<int>(nchannels * (int)ceil(nbits / (float)nchannels), 2);
  comps = 1000;
  @@ -2089,7 +2089,7 @@ void generateDescriptorSubsample(Mat& sampleList, Mat& comparisons, int nbits,
  samples = -1;
  for (int i = 0; i < npicks; i++) {
  - int k = rand() % (fullM.rows - i);
  + int k = rng(fullM.rows - i);
  if (i < 6) {
  // Force use of the coarser grid values and comparisons
  k = i;
  