This fixes all problems from the article "Checking OpenCV with PVS-Studio"
<http://www.viva64.com/en/b/0191/> that are not already fixed and are
not in 3rdparty or the legacy module.

The problems fixed are two instances of useless code and one instance
of unspecified behavior (right-shifting a negative number).

fix output matrix allocation in cv::subtract(cherry picked from commit 629461c8)

call dst.create(...) before using it(cherry picked from commit 4c66614e)

call dst.create(...) before using it

(cherry picked from commit e7e63fac)

(cherry picked from commit 09d25e11)

Looks like we don't actually use them; when creating precompiled headers
with Visual C++, a dummy .cpp is created at build time.

WITH_WINRT -> ENABLE_WINRT_MODE;
Some temporary char* replaced with Ptr<char>;
Build fix for regular WIN32;
Windows Platform SDK and MSVC search added to cmake;
Warinig fixes.

Fixed flann build with NEON;
Fixed Haming distance with NEON;
Honest cvRound for WinRT added;
cvRound test added;
Video IO with direct show disabled;