Merge remote-tracking branch 'origin/2.4' into merge-2.4

Conflicts:
	cmake/OpenCVDetectAndroidSDK.cmake
	cmake/OpenCVGenAndroidMK.cmake
	cmake/OpenCVModule.cmake
	cmake/templates/OpenCV.mk.in
	cmake/templates/OpenCVConfig.cmake.in
	doc/tutorials/imgproc/histograms/histogram_comparison/histogram_comparison.rst
	modules/cudabgsegm/src/cuda/mog.cu
	modules/imgproc/perf/opencl/perf_filters.cpp
	modules/imgproc/src/opencl/filterSep_singlePass.cl
	modules/nonfree/CMakeLists.txt
	modules/nonfree/perf/perf_precomp.hpp
	modules/ocl/perf/perf_haar.cpp
	modules/ocl/src/filtering.cpp
	modules/ocl/src/opencl/bgfg_mog.cl
	modules/superres/CMakeLists.txt
	modules/superres/src/btv_l1_cuda.cpp
	modules/superres/src/cuda/btv_l1_gpu.cu
	modules/superres/src/frame_source.cpp
	modules/superres/src/input_array_utility.cpp
	modules/superres/src/optical_flow.cpp
	modules/superres/src/precomp.hpp
	samples/gpu/CMakeLists.txt
	samples/gpu/brox_optical_flow.cpp
	samples/gpu/super_resolution.cpp

modules/flann/include/opencv2/flann/kmeans_index.h

@@ -758,10 +758,13 @@ private:
 
                     for (int k=0; k<indices_length; ++k) {
                         if (belongs_to[k]==j) {
-                            belongs_to[k] = i;
-                            count[j]--;
-                            count[i]++;
-                            break;
+                            // for cluster j, we move the furthest element from the center to the empty cluster i
+                            if ( distance_(dataset_[indices[k]], dcenters[j], veclen_) == radiuses[j] ) {
+                                belongs_to[k] = i;
+                                count[j]--;
+                                count[i]++;
+                                break;
+                            }
                         }
                     }
                     converged = false;