[move sift.cpp] sift: avoid inplace calls of GaussianBlur
[move sift.cpp] sift: avoid inplace calls of GaussianBlur

- should unlock IPP optimizations

original commit: https://github.com/opencv/opencv_contrib/commit/ce7c8f2646ccf3f5e657ab1241e22c0c32cd9d41

opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv