Make Hash.DELETE-KEY on a non-existing key 40% faster
Make Hash.DELETE-KEY on a non-existing key 40% faster

And much more memory churn friendly: there is no point creating a
scalar with the right descriptor, having it deconted on the return
anyway.  So just return the default value of the descriptor instead.

Mind you, I think returning Nil would be more correct: but that breaks
several spectests.

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