core(stat): register dispatched code, fix build

modules/core/CMakeLists.txt

 set(the_description "The Core Functionality")
 
 ocv_add_dispatched_file(mathfuncs_core SSE2 AVX AVX2)
+ocv_add_dispatched_file(stat SSE4_2 AVX AVX2)
 
 ocv_add_module(core
                "${OPENCV_HAL_LINKER_LIBS}"

modules/core/src/stat.cpp

@@ -4233,7 +4233,7 @@ cvNorm( const void* imgA, const void* imgB, int normType, const void* maskarr )
 
 namespace cv { namespace hal {
 
-static const uchar popCountTable[] =
+extern const uchar popCountTable[256] =
 {
     0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
     1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,

modules/core/src/stat.simd.hpp

@@ -5,6 +5,9 @@
 #include "opencv2/core/hal/intrin.hpp"
 
 namespace cv { namespace hal {
+
+extern const uchar popCountTable[256];
+
 CV_CPU_OPTIMIZATION_NAMESPACE_BEGIN
 
 // forward declarations