Remove obsolete FFMPEG versions support

* refactor: removed obsolete FFMPEG version support

 - Oldest available version via official FFMPEG repository mirror has tag v.0.5
 LIBAVFORMAT version for this tag is 52.31.0

* refactor: prefer std::min function to MIN macro

* refactor: use appropriate macro instead of manual version calculation

* refactor: remove macros for versions prior 0.5.15 release

* refactor: remove libavcodec macros for versions < 54.35.1 (default to Ubuntu 14.04)

* refactor: remove libavformat macro for versions < 54.20.4 (default ubuntu 14.04)

* refactor: remove libavutil macro for versions < 52.3.0 (default ubuntu 14.04)

* refactor: remove missed macros for libavcodec and libavformat

* refactor: remove unused _opencv_ffmpeg_free function

* build: add FFMPEG libraries versions checks

 - Add verbose message about what FFMPEG libraries are missing.
 - Add minimal versions check set to libav 9.20 release (default ubuntu 14.04) and FFMPEG 1.1.16 release.
   If the check is failed CMake produces user-friendly message instead of build error.

* fix: libavcodec version guard for AVDISCARD_NONINTRA

* fix: libav check of libavcodec version guard for AVDISCARD_NONINTRA

* fix: version check for AV_CODEC_FLAG_GLOBAL_HEADER

* fix: missing FFMPEG libraries output