privat/nit — pull request #730 by privat (2014-09-08 15:22:02+00:00)
Title: Chain implememtations

Change in engine so the selected implementation ise more abstract and has some kind of fall-back.

1. if intern or extern, try to get the specific implementation
2. else try to compile the body
3. else compile an error

The point is top prepare a future PR where intern and extern method could provide an alternative (slow or degraded) implementation.