PhotoFlow optimizations and benchmarks

I’ve just chatted with pippin:

< pippin>: elle is providing a good response on that forum, if someone wants to chip in with a comment from pippin…
< pippin>: I do not want babl to depend on an open-core project like lcms2, whoms performance is held hostage by the maintainer
< pippin>: using it for comparing accuracy/performance as well as for fallback for things not implemented, or not yet implemented is another matter