lang/scryer-prolog: New port

Scryer Prolog aims to become to ISO Prolog what GHC is to Haskell: an open
source industrial strength production environment that is also a
testbed for bleeding edge research in logic and constraint
programming, which is itself written in a high-level language.
PR: 286124
Reported by: Siva Mahadevan <me@svmhdvn.name>