* Convert lkpyramid from SSE SIMD to HAL - 90% faster on Power (VSX).
* Replace stores with reduce_sum. Rework to handle endianess correctly.
* Fix compiler warnings by casting values explicitly to shorts
* Switch to CV_SIMD128 compiler definition. Unroll loop to 8 elements since we've already loaded the data.
* Add debug build option to MacOs and iOS build scripts
* osx: allow selection of MACOSX_DEPLOYMENT_TARGET
* Add --debug_info flag to iOS and macOS builds for building with debug info
* jas_stream: Add definition for L_tmpnam if missing
uClibc-ng for some reason does not provide a definition when some
deprecated APIs are disabled. Value taken from the musl libc.
* 3rdparty: move uClibc-ng workaround into config file
Detected by clang trunk:
```
opencv/modules/core/src/ocl.cpp:4337:37: warning: object backing the pointer will be destroyed at the end of the full-expression [-Wdangling]
CV_OCL_CHECK_RESULT(retval, cv::format("clCreateBuffer(capacity=%lld) => %p", (long long int)entry.capacity_, (void*)entry.clBuffer_).c_str());
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
opencv/modules/core/src/ocl.cpp:193:42: note: expanded from macro 'CV_OCL_CHECK_RESULT'
if (0) { const char* msg_ = (msg); CV_UNUSED(msg_); /* ensure const char* type (cv::String without c_str()) */ } \
```
because `cv::format` yields a temporary std::string, and thus `msg_` points to a destroyed buffer.
* Fix the detection of XIMEA on Windows (when it has been installed by another user with administrative privileges, for example).
* Change the flow: we first try HKEY_CURRENT_USER key and, if empty, then try HKEY_LOCAL_MACHINE
Use 4x FMA chains to sum on SIMD 128 FP64 targets. On
x86 this showed about 1.4x improvement.
For PPC, do a full multiply (32x32->64b), convert to DP
then accumulate. This may be slightly less precise for
some inputs. But is 1.5x faster than the above which
is about 1.5x than the FMA above for ~2.5x speedup.
