ocl_minMaxIdx to call minmaxloc.cl for OpenCL 1.2+ only

This reverts commit a630ad73.

     * read vector at runtime
     * add enum

Add conditional compilation directives to enable uses of std::chrono on supported compilers. Use std::chrono::steady_clock as a source to retrieve current tick count and clock frequency.

Fixes opencv/opencv#6902.

This markdown file corresponds to the first link on the landing
page of OpenCV documentation.

This condition is the same as the line above.

* Fix compilation with non glibc.

_SC_NPROCESSORS_ONLN is non standard as defined on https://man7.org/linux/man-pages/man3/sysconf.3.html
It seems to only be on glibc, cf https://www.gnu.org/software/libc/manual/html_node/Processor-Resources.html

* Fix to defined(_SC_NPROCESSORS_ONLN)

/wrkdirs/usr/ports/graphics/opencv/work/opencv-4.5.5/modules/core/include/opencv2/core/vsx_utils.hpp:352:12: warning: 'vec_permi' macro redefined [-Wmacro-redefined]
#   define vec_permi(a, b, c) vec_xxpermdi(b, a, (3 ^ (((c) & 1) << 1 | (c) >> 1)))
           ^
/usr/lib/clang/13.0.0/include/altivec.h:13077:9: note: previous definition is here
#define vec_permi(__a, __b, __c)                                               \
        ^
/wrkdirs/usr/ports/graphics/opencv/work/opencv-4.5.5/modules/core/include/opencv2/core/vsx_utils.hpp:370:25: error: redefinition of 'vec_promote'
VSX_FINLINE(vec_dword2) vec_promote(long long a, int b)
                        ^
/usr/lib/clang/13.0.0/include/altivec.h:14604:1: note: previous definition is here
vec_promote(signed long long __a, int __b) {
^
/wrkdirs/usr/ports/graphics/opencv/work/opencv-4.5.5/modules/core/include/opencv2/core/vsx_utils.hpp:377:26: error: redefinition of 'vec_promote'
VSX_FINLINE(vec_udword2) vec_promote(unsigned long long a, int b)
                         ^
/usr/lib/clang/13.0.0/include/altivec.h:14611:1: note: previous definition is here
vec_promote(unsigned long long __a, int __b) {
^
/wrkdirs/usr/ports/graphics/opencv/work/opencv-4.5.5/modules/core/include/opencv2/core/hal/intrin_vsx.hpp:1045:22: error: call to 'vec_rsqrt' is ambiguous
{ return v_float32x4(vec_rsqrt(x.val)); }
                     ^~~~~~~~~
/usr/lib/clang/13.0.0/include/altivec.h:8472:34: note: candidate function
static vector float __ATTRS_o_ai vec_rsqrt(vector float __a) {
                                 ^
/wrkdirs/usr/ports/graphics/opencv/work/opencv-4.5.5/modules/core/include/opencv2/core/vsx_utils.hpp:362:29: note: candidate function
    VSX_FINLINE(vec_float4) vec_rsqrt(const vec_float4& a)
                            ^
/wrkdirs/usr/ports/graphics/opencv/work/opencv-4.5.5/modules/core/include/opencv2/core/hal/intrin_vsx.hpp:1047:22: error: call to 'vec_rsqrt' is ambiguous
{ return v_float64x2(vec_rsqrt(x.val)); }
                     ^~~~~~~~~
/usr/lib/clang/13.0.0/include/altivec.h:8477:35: note: candidate function
static vector double __ATTRS_o_ai vec_rsqrt(vector double __a) {
                                  ^
/wrkdirs/usr/ports/graphics/opencv/work/opencv-4.5.5/modules/core/include/opencv2/core/vsx_utils.hpp:365:30: note: candidate function
    VSX_FINLINE(vec_double2) vec_rsqrt(const vec_double2& a)
                             ^
1 warning and 4 errors generated.

The specific functions were added to altivec.h in LLVM's 1ff93618e58df210def48d26878c20a1b414d900, c3da07d216dd20fbdb7302fd085c0a59e189ae3d and 10cc5bcd868c433f9a781aef82178b04e98bd098.

All classes are registered in the scope that corresponds to C++
namespace or exported class.

Example:
`cv::ml::Boost` is exported as `cv.ml.Boost`
`cv::SimpleBlobDetector::Params` is exported as
`cv.SimpleBlobDetector.Params`

For backward compatibility all classes are registered in the global
module with their mangling name containing scope information.
Example:
`cv::ml::Boost` has `cv.ml_Boost` alias to `cv.ml.Boost` type

* Fix harmless MSAN error.

This is similar to https://github.com/opencv/opencv/pull/21527
A macro is also created to simplify the code.

* Declare fallback only once.

* Fix wrong MSAN errors.

Because Fortran is called in Lapack, MSAN does not think the memory
has been written even though it is the case.
MSAN does no support well cross-language memory analysis.

* Make a dedicated check.

hwcap should actually be long.

clang-cl defines both __clang__ and _MSC_VER, yet uses `#pragma GCC` to disable certain diagnostics.

At the time `-Wreturn-type-c-linkage` was reported by clang-cl.
This PR fixes this behavior by reordering defines.

- Add special case handling when submodule has the same name as parent
- `PyDict_SetItemString` doesn't steal reference, so reference count
  should be explicitly decremented to transfer object life-time
  ownership
- Add sanity checks for module registration input

We only use that value as uint64_t below anyway.