handle huge matrices correctly (#11505)

* make sure that the matrix with more than INT_MAX elements is marked as non-continuous, and thus all the pixel-wise functions process it correctly (i.e. row-by-row, not as a single row, where integer overflow may occur when computing the total number of elements)

modules/core/src/ocl.cpp

@@ -5681,8 +5681,6 @@ namespace cv {
 // three funcs below are implemented in umatrix.cpp
 void setSize( UMat& m, int _dims, const int* _sz, const size_t* _steps,
               bool autoSteps = false );
-
-void updateContinuityFlag(UMat& m);
 void finalizeHdr(UMat& m);
 
 } // namespace cv