Streamline ThreadPoolScheduler!xxxx-queue a bit
Streamline ThreadPoolScheduler!xxxx-queue a bit

- nqp::isconcrete instead of .DEFINITE
- nqp::elems instead of .elems

Gnouc/rakudo,lucasbuchala/rakudo,rakudo/rakudo,MasterDuke17/rakudo,rakudo/rakudo,lucasbuchala/rakudo,nbrown/rakudo,MasterDuke17/rakudo,softmoth/rakudo,tony-o/rakudo,rakudo/rakudo,labster/rakudo,lucasbuchala/rakudo,tbrowder/rakudo,labster/rakudo,softmoth/rakudo,tbrowder/rakudo,labster/rakudo,salortiz/rakudo,MasterDuke17/rakudo,tony-o/rakudo,tbrowder/rakudo,tbrowder/rakudo,tony-o/rakudo,salortiz/rakudo,salortiz/rakudo,salortiz/rakudo,tbrowder/rakudo,rakudo/rakudo,tbrowder/rakudo,Gnouc/rakudo,Gnouc/rakudo,labster/rakudo,Gnouc/rakudo,nbrown/rakudo,salortiz/rakudo,Gnouc/rakudo,nbrown/rakudo,labster/rakudo,tony-o/rakudo,lucasbuchala/rakudo,MasterDuke17/rakudo,nbrown/rakudo,labster/rakudo,tony-o/rakudo,softmoth/rakudo,tony-o/rakudo,nbrown/rakudo,lucasbuchala/rakudo,rakudo/rakudo,softmoth/rakudo,softmoth/rakudo,Gnouc/rakudo,rakudo/rakudo,salortiz/rakudo,MasterDuke17/rakudo,nbrown/rakudo,MasterDuke17/rakudo