Arm: fix the test failure of OCL_Imgproc/CLAHETest.Accuracy on ODROID-XU4 (#11409)
* fix the test failure of OCL_Imgproc/CLAHETest.Accuracy on ODROID-XU4
* avoid the race condition in the reduce
* imgproc(ocl): simplify CLAHE code
* remove unused class
If there are no OpenCL/UMat methods calls from application.
OpenCL subsystem is initialized:
- haveOpenCL() is called from application
- useOpenCL() is called from application
- access to OpenCL allocator: UMat is created (empty UMat is ignored) or UMat <-> Mat conversions are called
Don't call OpenCL functions if OPENCV_OPENCL_RUNTIME=disabled
(independent from OpenCL linkage type)
IPP can be switched on and off on runtime;
Optional implementation collector was added (switched off by default in CMake). Gathers data of implementation used in functions and report this info through performance TS;
TS modifications for implementations control;
Yes, it's as ludicrous as it sounds, but it's still true. Bizarrely,
the previous commit makes CLAHE run about 10% slower on Android, even
though it doesn't even touch any CLAHE code. Splitting it off fixes that,
although the reason it does is a mystery for the ages.
It's cleaner when it's in its own file, anyway. ;=]
