With this fix there is no need to add includes by using
`include_directories(${OpenCV_INCLUDE_DIRS})`. Directory will be added by
command `target_link_libraries(... ${OpenCV_LIBS})` automatically.

cvStereoRectify assumes that NULL is provided in case of no distCoeffs

The inner loop of the backward scan got the wrong initial "a".

- fix compilation for old libraries
- update codec/tag selection logic
- add documentation note about MP4 container tags