Main module headers are moved 1 level up

e.g. <opencv2/core/core.hpp> become <opencv2/core.hpp>

Also renamed <opencv2/core/opengl_interop.hpp> to <opencv2/core/opengl.hpp>

modules/stitching/perf/perf_stich.cpp

@@ -1,7 +1,7 @@
 #include "perf_precomp.hpp"
-#include "opencv2/highgui/highgui.hpp"
+#include "opencv2/highgui.hpp"
 #include "opencv2/core/internal.hpp"
-#include "opencv2/flann/flann.hpp"
+#include "opencv2/flann.hpp"
 #include "opencv2/opencv_modules.hpp"
 
 using namespace std;