Issue #2868

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

TIFF build was fixed;
Direct Show back-end was enabled;
More accurate guards implemented.

GPU module turned off;
TIFF support turned off;
Windows Managment and Video IO (VFW) turned off.

- added webp (lossy and lossless without alpha channel)
- added tests

This should be safe todo unless we are writing a signal handler.

The video(4) driver provides a Video4Linux2 compatible API for
various video peripherals. This patch propagates HAVE_VIDEOIO if
the sys/videoio.h include file is found, which is the signature of
video(4).

- added CMake toolchain file
- added WITH_NVCUVID flag

Sometimes information about dependencies causing disabling were loosed and it
was not possible to correctly display these dependencies in status report

 - exclude system paths from library search paths
 - remove hardcoded paths to compiler
 - enable compiling with 3d-parties
 - enable build as shared libraries

* added CMake toolchain file
* added WITH_NVCUVID flag