removed commented out obsolete functions
media-time class

+operator and comparators
media-time- returns difference between times in ms
fmpeg-cffi sws-get-cached-context takes sws-context as first parameter
ring-buffer with-ring-buffer support for optional paramter of element-factory

runs a constructor for each array element, useful if each array if a struct
covers also make-ring-buffer, make-array -context
packages export of media-time to allow use in ffmpeg package
compile implementation of run-ffmpeg-in for video-params class

calls scale-frame function after frame is decoded