core: rework code locality

- to reduce binaries size of FFmpeg Windows wrapper
- MinGW linker doesn't support -ffunction-sections (used for FFmpeg Windows wrapper)
- move code to improve locality with its used dependencies
- move UMat::dot() to matmul.dispatch.cpp (Mat::dot() is already there)
- move UMat::inv() to lapack.cpp
- move UMat::mul() to arithm.cpp
- move UMat:eye() to matrix_operations.cpp (near setIdentity() implementation)
- move normalize(): convert_scale.cpp => norm.cpp
- move convertAndUnrollScalar(): arithm.cpp => copy.cpp
- move scalarToRawData(): array.cpp => copy.cpp
- move transpose(): matrix_operations.cpp => matrix_transform.cpp
- move flip(), rotate(): copy.cpp => matrix_transform.cpp (rotate90 uses flip and transpose)
- add 'OPENCV_CORE_EXCLUDE_C_API' CMake variable to exclude compilation of C-API functions from the core module
- matrix_wrap.cpp: add compile-time checks for CUDA/OpenGL calls
- the steps above allow to reduce FFmpeg wrapper size for ~1.5Mb (initial size of OpenCV part is about 3Mb)

backport is done to improve merge experience (less conflicts)
backport of commit: 65eb946756

modules/core/src/mathfuncs.cpp

@@ -1637,6 +1637,9 @@ void patchNaNs( InputOutputArray _a, double _val )
 
 }
 
+
+#ifndef OPENCV_EXCLUDE_C_API
+
 CV_IMPL float cvCbrt(float value) { return cv::cubeRoot(value); }
 CV_IMPL float cvFastArctan(float y, float x) { return cv::fastAtan2(y, x); }
 
@@ -1720,6 +1723,7 @@ CV_IMPL int cvCheckArr( const CvArr* arr, int flags,
     return cv::checkRange(cv::cvarrToMat(arr), (flags & CV_CHECK_QUIET) != 0, 0, minVal, maxVal );
 }
 
+#endif  // OPENCV_EXCLUDE_C_API
 
 /*
   Finds real roots of cubic, quadratic or linear equation.
@@ -2015,6 +2019,8 @@ double cv::solvePoly( InputArray _coeffs0, OutputArray _roots0, int maxIters )
 }
 
 
+#ifndef OPENCV_EXCLUDE_C_API
+
 CV_IMPL int
 cvSolveCubic( const CvMat* coeffs, CvMat* roots )
 {
@@ -2034,6 +2040,7 @@ void cvSolvePoly(const CvMat* a, CvMat *r, int maxiter, int)
     CV_Assert( _r.data == _r0.data ); // check that the array of roots was not reallocated
 }
 
+#endif  // OPENCV_EXCLUDE_C_API
 
 
 // Common constants for dispatched code