message: Using environment variable to store capture options
  * Using environment variable to store options parsed by av_dict_parse_string(ENV{OPENCV_FFMPEG_CAPTURE_OPTIONS}, ";", "|")
  * Adding missing mandatory flags parameter
  * Guarding against missing function via LIBAVUTIL version
  * Code review fixes
  Copy/paste error due to coder mistake reverted
  Proper version checking for LIBAVUTIL_BUILD
diff: @@ -781,7 +781,23 @@ bool CvCapture_FFMPEG::open( const char* _filename )
  #endif
  #if LIBAVFORMAT_BUILD >= CALC_FFMPEG_VERSION(52, 111, 0)
  +#ifndef NO_GETENV
  + char* options = getenv("OPENCV_FFMPEG_CAPTURE_OPTIONS");
  + if(options == NULL)
  + {
  + av_dict_set(&dict, "rtsp_transport", "tcp", 0);
  + }
  + else
  + {
  +#if LIBAVUTIL_BUILD >= (LIBAVUTIL_VERSION_MICRO >= 100 ? CALC_FFMPEG_VERSION(52, 17, 100) : CALC_FFMPEG_VERSION(52, 7, 0))
  + av_dict_parse_string(&dict, options, ";", "|", 0);
  +#else
  av_dict_set(&dict, "rtsp_transport", "tcp", 0);
  +#endif
  + }
  +#else
  + av_dict_set(&dict, "rtsp_transport", "tcp", 0);
  +#endif
  int err = avformat_open_input(&ic, _filename, NULL, &dict);
  #else
  int err = av_open_input_file(&ic, _filename, NULL, 0, NULL);
  