Also:
- Silence clang warnings about unsupported command line arguments
- Add diagnostic print to calib3d test
- Fixed perf test relative error check
- Fix iOS build problem

Conflicts:
	modules/contrib/include/opencv2/contrib/retina.hpp

Conflicts:
	cmake/OpenCVFindLibsVideo.cmake

The two functions featuring nNull are not particularly needed, so
I simply removed them.

Conflicts:
	modules/highgui/src/cap_msmf.hpp

Conflicts:
	modules/gpu/perf/perf_imgproc.cpp

Cast a long integer to double explicitly.

Conflicts:
	modules/python/src2/cv2.cpp

Cast some matrix sizes to type int.

Change some vector mask types to unsigned.

Conflicts:
	modules/core/src/arithm.cpp

Conflicts:
	modules/highgui/src/window_QT.cpp

A difference of two pointers was casted to unsigned which can lead to
overflow on 64-bit systems.

If used cl compiler, but generator is not Visual Studio e.g. Ninja,
enable FS option to prevent blocking PDB file in multithreaded build.

The use of built-in CMAKE_CURRENT_LIST_DIR requires at least
CMake 2.8.3. This fix properly defines the variable to allow its
use in versions < 2.8.3 as well.

Fixes issue #4205.

Exclude >= 2.8.3 from reimplementation of CMAKE_CURRENT_LIST_DIR

This avoids violation of possible future CMake policy checks
regarding reserved/read-only variables.

Conflicts:
	doc/tutorials/imgproc/imgtrans/hough_lines/hough_lines.rst

fixed mjpeg encoder so that libjpeg-based decoder does not complain on extra bytes in the end of stream

It took me a while to figure out what was meant with

    OpenCV Error: Assertion failed (i < 0) in getMat

While searching for this error message I found [a list of error
messages](https://adventuresandwhathaveyou.wordpress.com/2014/03/14/opencv-error-messages-suck/)
which also explained what the problem was: The data type for `rvecs` was
not a simple `cv::Mat` but a `std::vector<cv::Mat>`.

After I fixed that, I got the next error message:

    OpenCV Error: Assertion failed (ni > 0 && ni == ni1) in
    collectCalibrationData, file
    /build/buildd/opencv-2.4.9+dfsg/modules/calib3d/src/calibration.cpp,
    line 3193

The problem here was that my data type for the `objectPoints` was just
`vector<Vec3f>` and not `vector<vector<Vec3f>>`.

In order to save other people the time looking for this, I added
explicit examples of the needed data types into the documentation of the
function. I had to re-read the current version a couple of times until I
can read the needed levels of `vector<>`. Having this example would have
really helped me there.