Make sure method `submethod_table` exists.
Make sure method `submethod_table` exists.

WALK must not attempt fetching submethods from typeobjects not
supporting them. Primarily this will help when inheriting from
NQP-world classes or consuming NQP-world roles.

MasterDuke17/rakudo,labster/rakudo,tbrowder/rakudo,tony-o/rakudo,MasterDuke17/rakudo,tony-o/rakudo,salortiz/rakudo,salortiz/rakudo,MasterDuke17/rakudo,rakudo/rakudo,tbrowder/rakudo,MasterDuke17/rakudo,labster/rakudo,tbrowder/rakudo,MasterDuke17/rakudo,tony-o/rakudo,tbrowder/rakudo,salortiz/rakudo,tbrowder/rakudo,salortiz/rakudo,labster/rakudo,rakudo/rakudo,rakudo/rakudo,tbrowder/rakudo,rakudo/rakudo,tony-o/rakudo,labster/rakudo,tony-o/rakudo,tony-o/rakudo,salortiz/rakudo,MasterDuke17/rakudo,labster/rakudo,rakudo/rakudo,salortiz/rakudo,labster/rakudo,rakudo/rakudo