c_examples: add sdl_v4l_video program
c_examples: implify Makefile
c_examples/sdl_v4l_video: print elapsed time before first captured frame
c_examples/sdl_v4l_video: ensure video ratio is kept accross resizing
python_cffi: add numpy matrix strides usecase
python_example: merge with python_cffi
python_examples: merge with python_matplotlib_tests
python_examples: make pylint happy