core: dispatch matmul

- gemm: keep baseline only (lapack is 10x+ faster, lets reduce binary size)
- transform / distTransform
- scaleAdd (32f/64f only)
- Mahalanobis: keep baseline only (no perf tests)
- mulTransposed: keep baseline only (no perf tests)
- dot

modules/core/CMakeLists.txt

@@ -6,6 +6,7 @@ ocv_add_dispatched_file(arithm SSE2 SSE4_1 AVX2 VSX3)
 ocv_add_dispatched_file(convert SSE2 AVX2)
 ocv_add_dispatched_file(convert_scale SSE2 AVX2)
 ocv_add_dispatched_file(count_non_zero SSE2 AVX2)
+ocv_add_dispatched_file(matmul SSE2 AVX2)
 ocv_add_dispatched_file(sum SSE2 AVX2)
 
 # dispatching for accuracy tests

modules/core/include/opencv2/core/cv_cpu_dispatch.h

@@ -15,6 +15,7 @@
 #define CV_CPU_OPTIMIZATION_NAMESPACE cpu_baseline
 #define CV_CPU_OPTIMIZATION_NAMESPACE_BEGIN namespace cpu_baseline {
 #define CV_CPU_OPTIMIZATION_NAMESPACE_END }
+#define CV_CPU_BASELINE_MODE 1
 #endif