Parse -codecs output from 1.x-4.x builds of FFmpeg

[svjson]

The output format of the flags column of codecs have changed starting with FFMpeg 1.0, and so ffmpeg.codecs() returns an empty list.

This pull request uses a different regex pattern for parsing the -codecs output of ffmpeg depending on -version.

[bramp]

Sorry for the long delay. This change looks great, thanks for writing it, and sorry I never reviewed it. It looks like I accepted 9a5507c which just fixed it by moving to the latest format. But this pull request looks better by trying the old and new.

If you are willing I'll accept this if you can resolve the merge conflicts.