[m-rev.] for possible review: make ':- external' a pragma

[Julien Fischer]

Hi Zoltan,

I will take a look at it this afternoon.

Cheers,
Julien.

On Wed, 22 Jul 2015, Zoltan Somogyi wrote:

> Is anyone interested in reviewing this? If yes, I will wait for the review,
> and work on something else. If not, I will commit it and build on it.
>
> Zoltan.