added ensureSizeIsEnough into gpu module, updated reduction methods

modules/gpu/include/opencv2/gpu/gpu.hpp

@@ -252,9 +252,13 @@ namespace cv
     #include "GpuMat_BetaDeprecated.hpp"
 #endif
 
-        //! creates continuous GPU matrix
+        //! Creates continuous GPU matrix
         CV_EXPORTS void createContinuous(int rows, int cols, int type, GpuMat& m);
 
+        //! Ensures that size of the given matrix is not less than (rows, cols) size
+        //! and matrix type is match specified one too
+        CV_EXPORTS void ensureSizeIsEnough(int rows, int cols, int type, GpuMat& m);
+
         //////////////////////////////// CudaMem ////////////////////////////////
         // CudaMem is limited cv::Mat with page locked memory allocation.
         // Page locked memory is only needed for async and faster coping to GPU.

modules/gpu/include/opencv2/gpu/matrix_operations.hpp

@@ -364,6 +364,10 @@ inline GpuMat createContinuous(Size size, int type)
     return m;
 }
 
+inline void ensureSizeIsEnough(Size size, int type, GpuMat& m)
+{
+    ensureSizeIsEnough(size.height, size.width, type, m);
+}
 
 
 ///////////////////////////////////////////////////////////////////////
@@ -401,6 +405,7 @@ inline CudaMem::CudaMem(const Mat& m, int _alloc_type) : flags(0), rows(0), cols
 inline CudaMem::~CudaMem()
 {
     release();
+
 }
 
 inline CudaMem& CudaMem::operator = (const CudaMem& m)