Merge remote-tracking branch 'origin/2.4' into merge-2.4

Conflicts:
	modules/contrib/src/retina.cpp
	modules/core/include/opencv2/core/mat.hpp
	modules/core/src/algorithm.cpp
	modules/core/src/arithm.cpp
	modules/features2d/src/features2d_init.cpp
	modules/gpu/include/opencv2/gpu/gpu.hpp
	modules/gpu/perf/perf_imgproc.cpp
	modules/imgproc/src/generalized_hough.cpp
	modules/ocl/include/opencv2/ocl/ocl.hpp
	modules/video/src/tvl1flow.cpp
	modules/video/src/video_init.cpp

modules/highgui/src/precomp.hpp

@@ -58,6 +58,14 @@
 #include <assert.h>
 
 #if defined WIN32 || defined WINCE
+    #if !defined _WIN32_WINNT
+        #ifdef HAVE_MSMF
+            #define _WIN32_WINNT 0x0600 // Windows Vista
+        #else
+            #define _WIN32_WINNT 0x0500 // Windows 2000
+        #endif
+    #endif
+
     #include <windows.h>
     #undef small
     #undef min