Add a unit test for the standard `sub_atom/5` predicate that catches a bug in B-Prolog 8.1
Add a unit test for the standard `sub_atom/5` predicate that catches a bug in B-Prolog 8.1

LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3