Instead of having to configure PPs in code, this allows us and embedding programs not to worry about imports or finer details, similarly to how we handle IEs.
utils is large enough without these compatibility functions.
Everything that is present in newer versions of Python (i.e. with dev Python it's just an import) goes into compat.py .
Everything else (i.e. youtube-dl-specific helpers) goes into utils.py .
Affects the ffmpeg post processors, if ‘--prefer-ffmpeg’ is given and both avconv and ffmpeg are installed, it will use ffmpeg. Otherwise it will follow the old behaviour.