* Fixed bug that made cuda::filter give corrupted output when different filters called in different threads. This was due to use of global texture variable shared by all filters.

* REV: fixed tab issue for opencv coding style...

  * avoid race condition

Found via `codespell -q 3 -I ../opencv-whitelist.txt --skip="./3rdparty"`

cuda_canny : multi stream safety (#11483)

* CUDA_ImgProc/Canny Asynchronous test

* cuda_canny : multi stream safety (1/3)

- Convert global variable canny::counter to class local variable

* cuda_canny : multi stream safety (2/3)

- Use texture objects rather than texture reference for cc >= 3.0,
  since texture reference must be declared as a static global variable
  which results in race condition when ran concurrently

* cuda_canny : multi stream safety (3/3)

- Refrain from using global variable in row_filter and column_filter
  (converts column_filter::c_kernel and row_filter::c_kernel to local
  variables)

* Fixes #11193

Found via `codespell`

Removed redundant precompiled header include

Speedup MedianFilter::apply(), avoid to newly create the two GpuMat every time calling filter->apply(), which is very time consuming.

* remove overloads with explicit buffer, now BufferPool is used
* added async versions for all reduce functions

Conflicts:
	modules/core/include/opencv2/core/cuda.hpp
	modules/cudacodec/src/thread.cpp
	modules/cudacodec/src/thread.hpp
	modules/superres/perf/perf_superres.cpp
	modules/superres/src/btv_l1_cuda.cpp
	modules/superres/src/optical_flow.cpp
	modules/videostab/src/global_motion.cpp
	modules/videostab/src/inpainting.cpp
	samples/cpp/stitching_detailed.cpp
	samples/cpp/videostab.cpp
	samples/gpu/stereo_multi.cpp