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.

On Windows, the tmpnam function returns a temp filename in the current directory, which has a prepended backslash '\\'.
This subsequently fails the open function.

This patch creates a proper temp filename in the temp folder and makes unlike work by opening the file as short-lived.

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

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).

[~] fixed warning in featuers2d under windows (can't generate assignment operator)