Detailed description for my proposal can be found here
https://github.com/opencv/opencv/issues/14128

* Add flushing to printing number of processed positive/negative samples so that user is informed of updates quickly.

* use flush C api instead of C++ api

backport 997b7b18

* integrated the new C++ persistence; removed old persistence; most of OpenCV compiles fine! the tests have not been run yet

* fixed multiple bugs in the new C++ persistence

* fixed raw size of the parsed empty sequences

* [temporarily] excluded obsolete applications traincascade and createsamples from build

* fixed several compiler warnings and multiple test failures

* undo changes in cocoa window rendering (that was fixed in another PR)

* fixed more compile warnings and the remaining test failures (hopefully)

* trying to fix the last little warning

Relevant guards can be found in
https://github.com/opencv/opencv/blob/ef5579dc8667e5eb5e149acc4af898421eed99da/modules/features2d/src/kaze/AKAZEConfig.h#L8
and
https://github.com/opencv/opencv/blob/ef5579dc8667e5eb5e149acc4af898421eed99da/modules/ml/include/opencv2/ml.hpp#L44

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

* apps: add Win32 friendly opencv_version app

Improve experience of launching app from explorer:
- application just flash (open/close) the console window
Suggested Win32 application flavor additionally shows MessageBox
and waits for User interaction.

* cmake: added unified application creation function

Improve experience of launching app from explorer:
- application just flash (open/close) the console window
Suggested Win32 application flavor additionally shows MessageBox
and waits for User interaction.

- build "opencv_version" only: `cmake -DBUILD_APPS_LIST=version ...`
- option 'BUILD_opencv_apps' should be 'ON'

destroyWindow was called twice during completion of the
annotation procedure, resulting in a crash, and failure to write
an output file

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

fix missing "opencv2/core/opencl" headers from core module (updated install list)

* update createsamples

adds command-line option -rngseed
replaces rand() -> theRNG()

* Update utility.cpp

* apps(createsamples): fix warpPerspective pixels access bug

Implementation of bit-exact resize. Internal calls to linear resize updated to use bit-exact version. (#9468)

Added a couple of comments to the interface of traincascade.cpp in order to tell user about the usage of traincascade.cpp file and to learn how Github submitting works