Initial Windows RT support commit.
GPU module turned off;
TIFF support turned off;
Windows Managment and Video IO (VFW) turned off.
Multiple Windows RT fixes

TIFF build was fixed;
Direct Show back-end was enabled;
More accurate guards implemented.
More accurate guards for WinRT features in CMake.
Highgui tests for GUI disabled for WinRT;
Warnings fix;
Multiple fixes for WinRT

Fixed flann build with NEON;
Fixed Haming distance with NEON;
Honest cvRound for WinRT added;
cvRound test added;
Video IO with direct show disabled;
use perf test replace performance sample
Video IO tests turned off for ARM WinRT.
HAVE_WIN32UI and HAVE_VFW checks and defines added.
Perf tests for Video IO on WInRT fixed.
fixed bug in TVL1 optical flow:

initial optical flow was not cleaned during the second call
Fix typo leading to heap corruption in OutputArray::create
Merge pull request #723 from virtuald:2.4
Merge pull request #721 from jet47:tvl1-bug-fix
fixed misprint in MatOp::augAssignXor
removed unnecessary tmp variable (convertTo can work in-place)
fixed misprint in icvCreateIsometricImage
fixed misprint in imgwarp.cpp
removed duplication
fixed potential dereference of null pointer
fixed incorrect sizeof() expression in CvCaptureCAM_VFW::open