Implement GArik's comments

Remove unnecessary c_str()

Fix brace position

Supported ONNX Squeeze, ReduceL2 and Eltwise::DIV

* Support eltwise div

* Fix test

* OpenCL support added

* refactoring

* fix code style

* Only squeeze with axes supported

Fix an error during Windows installation caused by trying to create the already existing Build directory. Also excluding intermediate steps for Install directory creation.

* Grammar fixes for python core operations docs

* fixed whitespace error

* reverted changes

Signed-off-by: SSE4 <tomskside@gmail.com>

It's not an error if some OpenCL platform has no devices. This makes
OpenCL device detection work correctly in the following scenario:

$ OPENCV_OPENCL_DEVICE=:GPU: ./opencv_test_dnn

OpenCV version: 4.1.2-dev
OpenCV VCS version: 4.1.2-80-g467748ee98-dirty
Build type: Debug
Compiler: /usr/bin/g++  (ver 7.4.0)
Parallel framework: pthreads
CPU features: SSE SSE2 SSE3 *SSE4.1 *SSE4.2 *FP16 *AVX *AVX2 *AVX512-SKX?
Intel(R) IPP version: ippIP AVX2 (l9) 2019.0.0 Gold (-) Jul 24 2018
OpenCL Platforms:
    AMD Accelerated Parallel Processing
    Portable Computing Language
        CPU: pthread-AMD Ryzen 7 2700X Eight-Core Processor (OpenCL 1.2 pocl HSTR: pthread-x86_64-pc-linux-gnu-znver1)
    NVIDIA CUDA
        dGPU: GeForce GTX 1080 (OpenCL 1.2 CUDA)
Current OpenCL device:
    Type = dGPU
    Name = GeForce GTX 1080
    Version = OpenCL 1.2 CUDA
    Driver version = 430.26

* Convert moments in tile algorithms to HAL (1.3x faster for VSX).

* Adding NEON code back in for non 64-bit platforms.

* Remove floats from post processing.

- added removal of temporary file

* Reduce code nesting
* Drop redundant .c_str() calls

Correct stereoRectify documentation

Fix wrong definition of viz::Color::navy()

Clarify stereoRectify() doc

The function stereoRectify() takes as input a coordinate transform between two cameras. It is ambiguous how it goes. I clarified that it goes from the second camera to the first.

* Use FlsAlloc/FlsFree/FlsGetValue/FlsSetValue instead of TlsAlloc/TlsFree/TlsGetValue/TlsSetValue to implment TLS value cleanup when thread has been terminated on Windows Vista and above

* Fix 32-bit build

* Fixed calling convention of cleanup callback

* WINAPI changed to NTAPI

* Use proper guard macro

* Vectorize flipHoriz and flipVert functions.

* Change v_load_mirror_1 to use vec_revb for VSX

* Only use vec_revb in ISA3.0

* Removing vec_revb code since some of the older compilers don't fully support it.

* Use new v_reverse intrinsic and cleanup code.

* Ensure there are no alignment issues with copies

Parallelize pyrDown & calcSharrDeriv

* ::pyrDown has been parallelized

* CalcSharrDeriv parallelized

* Fixed whitespace

* Set granularity based on amount of threads enabled

* Granularity changed to cv::getNumThreads, now each thread should receive 1/n sized stripes

* imgproc: move PyrDownInvoker<CastOp>::operator() implementation

* imgproc(pyramid): remove syloopboundary()

* video: SharrDerivInvoker replace 'Mat*' => 'Mat&' fields

* Changes disparity image to float representation
Signed-off-by: Connor James Smith <cjs.connor.smith@gmail.com>

* samples: update disparity multiplier handling in stereo_match.cpp