* Use Intel TBB's task arena if possible

 calib3d: add stereoCalibrateExtended (#10667)

* cvCalibrateCamera2Internal: simplify per view error computation

* calib3d: add stereoCalibrateExtended

- allow CALIB_USE_EXTRINSIC_GUESS
- returns per view errors

* calib3d: add stereoCalibrateExtended test

* cmake: enable CPU dispatching for AVX512 (SKX)

* cmake: update handling of unsupported flags/modes

Signed-off-by: Li Peng <peng.li@intel.com>

Signed-off-by: Li Peng <peng.li@intel.com>

allows Stitcher to be used for scans from within python.
I had to use very strange notation because I couldn't export the `enum`
`Mode` making the Cpython generated code unable to compile.

```c++
class Stitcher {
public:
enum Mode
    {
        PANORAMA = 0,
        SCANS = 1,
    };
...
```

Also removed duplicate code from the `createStitcher` function making
use of the `Stitcher::create` function

* hogsvm compatibility with python3

* add HAL for FAST

* add new interface

* persistence: replace arbitrary limit of cn to 4 by CV_CN_MAX

* python: added persistence test, remove temp files

* fixup! python: added persistence test, remove temp files

* fixup! python: added persistence test, remove temp files

- reduce scope of i,k,j variables
- use cv::AutoBuffer
- template<bool onlyDistance> class KMeansDistanceComputer
- eliminate manual unrolling: CV_ENABLE_UNROLLED

- don't use RNG for "task size" parameters (N, K, dims)
- add "good" kmeans test data (without singularities: K > unique points)

* Bit-exact implementation of GaussianBlur smoothing

* Added universal intrinsics based implementation for bit-exact CV_8U GaussianBlur smoothing.

* Added parallel_for to evaluation of bit-exact GaussianBlur

* Added custom implementations for 3x3 and 5x5 bit-exact GaussianBlur

* Fix for QT image window rectangle

* Update window_QT.h

* Update window_QT.cpp

* trailing whitespace

* highgui: fix QT getWindowImageRect()