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

Merged pull requests:
	#890 from caorong:patch-1
	#893 from jet47:gpu-arm-fixes
	#933 from pengx17:2.4_macfix_cont
	#935 from pengx17:2.4_filter2d_fix
	#936 from bitwangyaoyao:2.4_perf
	#937 from bitwangyaoyao:2.4_fixPyrLK
	#938 from pengx17:2.4_surf_sample
	#939 from pengx17:2.4_getDevice
	#940 from SpecLad:autolock
	#941 from apavlenko:signed_char
	#946 from bitwangyaoyao:2.4_samples2
	#947 from jet47:fix-gpu-arm-build
	#948 from jet47:cuda-5.5-support
	#952 from SpecLad:jepg
	#953 from jet47:fix-bug-3069
	#955 from SpecLad:symlink
	#957 from pengx17:2.4_fix_corner_detector
	#959 from SpecLad:qt4-build
	#960 from SpecLad:extra-modules

Conflicts:
	modules/core/include/opencv2/core/core.hpp
	modules/gpu/CMakeLists.txt
	modules/gpu/include/opencv2/gpu/device/vec_math.hpp
	modules/gpu/perf/perf_video.cpp
	modules/gpuimgproc/src/cuda/hough.cu
	modules/ocl/include/opencv2/ocl/ocl.hpp
	modules/ocl/src/pyrlk.cpp
	samples/gpu/driver_api_multi.cpp
	samples/gpu/driver_api_stereo_multi.cpp
	samples/ocl/surf_matcher.cpp

modules/ocl/include/opencv2/ocl.hpp

@@ -708,6 +708,8 @@ namespace cv
         }
 
         //! applies non-separable 2D linear filter to the image
+        //  Note, at the moment this function only works when anchor point is in the kernel center
+        //  and kernel size supported is either 3x3 or 5x5; otherwise the function will fail to output valid result
         CV_EXPORTS void filter2D(const oclMat &src, oclMat &dst, int ddepth, const Mat &kernel,
                                  Point anchor = Point(-1, -1), int borderType = BORDER_DEFAULT);