Constrain Enumeration.succ/.pred to instances
Constrain Enumeration.succ/.pred to instances

pre- https://github.com/rakudo/rakudo/pull/1156 type objects would
just die with X::Parameter::InvalidConcreteness but now they return
weird results.

Constrain to instances, to restore the ::InvalidConcreteness throwage
we had before.

Gnouc/rakudo,usev6/rakudo,usev6/rakudo,usev6/rakudo,softmoth/rakudo,nbrown/rakudo,softmoth/rakudo,labster/rakudo,salortiz/rakudo,tony-o/rakudo,tbrowder/rakudo,awwaiid/rakudo,MasterDuke17/rakudo,usev6/rakudo,Gnouc/rakudo,tony-o/rakudo,rakudo/rakudo,nbrown/rakudo,nbrown/rakudo,lucasbuchala/rakudo,tony-o/rakudo,tbrowder/rakudo,rakudo/rakudo,salortiz/rakudo,tony-o/rakudo,jonathanstowe/rakudo,raydiak/rakudo,lucasbuchala/rakudo,rakudo/rakudo,jonathanstowe/rakudo,MasterDuke17/rakudo,awwaiid/rakudo,awwaiid/rakudo,tbrowder/rakudo,jonathanstowe/rakudo,Gnouc/rakudo,MasterDuke17/rakudo,jonathanstowe/rakudo,lucasbuchala/rakudo,salortiz/rakudo,tbrowder/rakudo,lucasbuchala/rakudo,Gnouc/rakudo,MasterDuke17/rakudo,raydiak/rakudo,Gnouc/rakudo,labster/rakudo,labster/rakudo,lucasbuchala/rakudo,raydiak/rakudo,rakudo/rakudo,nbrown/rakudo,rakudo/rakudo,MasterDuke17/rakudo,labster/rakudo,softmoth/rakudo,nbrown/rakudo,softmoth/rakudo,MasterDuke17/rakudo,tony-o/rakudo,tbrowder/rakudo,rakudo/rakudo,salortiz/rakudo,usev6/rakudo,softmoth/rakudo,awwaiid/rakudo,salortiz/rakudo,nbrown/rakudo,tony-o/rakudo,jonathanstowe/rakudo,labster/rakudo,salortiz/rakudo,Gnouc/rakudo,labster/rakudo,awwaiid/rakudo,tbrowder/rakudo,raydiak/rakudo