(2.4) Backports from master branch (#7854)

Pdb file support was changed in CMake 2.8.12, support was added in CMake 3.1.0 to work around the problems created by the change introduced in CMake 2.8.12.

 - Resolved GET_ENV and input type incompatibility
 - Made libjpeg compile for WINRT. So does imgcodecs module.
 - Updated .gitignore (log, tlog)

- Substituted HAVE_WINRT with WINRT
- Fixed compilation issues in ocl.cpp and parallel.cpp
- Fixed compiler issue for WP8: "C2678: binary '+' : no operator found which takes a left-hand - Fixed gitignore
- Added #ifdef HAVE_OPENCL to remove compiler warnings in ocl.cpp
- Used NO_GETENV similar to '3rdparty\libjpeg\jmemmgr.c;
- Added ole32.lib for core module (for WindowsStore 8.0 builds)
- Made OpenCV_ARCH aware of ARM
Signed-off-by: Maxim Kostin <v-maxkos@microsoft.com>

Improve comments to indicate actual usage of WORDS_BIGENDIAN where
it is tested with #ifdef rather than #if

Use correct integer types for arguments to TIFFGetField to avoid corruption
of values and failed loads of TIFF file when using cv::imread().

Added test where both big and little endian TIFF files are read using imread().

Fixed build of 3rdparty libtiff on big endian hosts.

Reduced memory required during decode_tile16384x16384 test by not converting
large grayscale test image to color image during read.

(cherry picked from commit b75cbfde)

Conflicts:

	cmake/OpenCVModule.cmake

Allow to build samples via OpenCV binaries from distribution package
(find_package with OpenCV_DIR).

They're not listed in the documentation for the FindZLIB module,
so we shouldn't use them unless necessary.

* No /arch:SSE3 in MSVC
* Warnings fixed or suppressed

Suppressed hundreds of useless MSVC warnings (can be reenabled setting cmake variable ENABLE_NOISY_WARNINGS to ON). Fixed some of remaining warnings.

* Fixed zlib search.
* Fixed compiler/linker flags caching bug.
* Fixed OpenCVConfig.cmake generation (currently tested only on Unix).