fixed some compile-time problems (under Ubuntu)

modules/gpu/src/split_merge.cpp

@@ -100,7 +100,8 @@ namespace cv { namespace gpu { namespace split_merge
             for(size_t i = 0; i < n; ++i)
                 src_as_devmem[i] = src[i];
 
-            split_merge::merge_caller(src_as_devmem, (DevMem2D)dst, 
+            DevMem2D dst_as_devmem(dst);
+            split_merge::merge_caller(src_as_devmem, dst_as_devmem,
                                       total_channels, CV_ELEM_SIZE(depth),
                                       stream);
         }   
@@ -130,7 +131,8 @@ namespace cv { namespace gpu { namespace split_merge
         for (int i = 0; i < num_channels; ++i)
             dst_as_devmem[i] = dst[i];
 
-        split_merge::split_caller((DevMem2D)src, dst_as_devmem, 
+        DevMem2D src_as_devmem(src);
+        split_merge::split_caller(src_as_devmem, dst_as_devmem,
                                   num_channels, src.elemSize1(), 
                                   stream);
     }

tests/gpu/src/imgproc_gpu.cpp

@@ -379,7 +379,7 @@ struct CV_GpuNppImageIntegralTest : public CV_GpuImageProcTest
 {
     CV_GpuNppImageIntegralTest() : CV_GpuImageProcTest( "GPU-NppImageIntegral", "integral" ) {}
 
-    int CV_GpuNppImageIntegralTest::test(const Mat& img)
+    int test(const Mat& img)
     {
         if (img.type() != CV_8UC1)
         {