Fix cv::CommandLineParser::check() documentation

- moved to table title
- can be restored via '--show_units' option
- fix microseconds: mks -> us

* 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

OpenCV pthreads-based implementation changes:
- rework worker threads pool, allow to execute job by the main thread too
- rework synchronization scheme (wait for job completion, threads 'pong' answer is not required)
- allow "active wait" (spin) by worker threads and by the main thread
- use _mm_pause() during active wait (support for Hyper-Threading technology)
- use sched_yield() to avoid preemption of still working other workers
- don't use getTickCount()
- optional builtin thread pool profiler (disabled by compilation flag)

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

Signed-off-by: NLi 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