added dedicated <modname>_init.cpp files with initModule_<modname>() functions and all the relevant structures; made BackgroundSubtractorMOG/MOG2 derivatives from Algorithm; cleaned up MOG2 implementation and made it multi-threaded.

modules/core/include/opencv2/core/core.hpp

@@ -2020,6 +2020,15 @@ public:
 };
 
     
+typedef void (*BinaryFunc)(const uchar* src1, size_t step1,
+                           const uchar* src2, size_t step2,
+                           uchar* dst, size_t step, Size sz,
+                           void*);
+
+CV_EXPORTS BinaryFunc getConvertFunc(int sdepth, int ddepth);
+CV_EXPORTS BinaryFunc getConvertScaleFunc(int sdepth, int ddepth);
+CV_EXPORTS BinaryFunc getCopyMaskFunc(size_t esz);    
+    
 //! swaps two matrices
 CV_EXPORTS void swap(Mat& a, Mat& b);