Revert "Optimizer: Direct assignment between native vars don't need refs"
Revert "Optimizer: Direct assignment between native vars don't need refs"

It causes problems with assigning to rw arguments. Need a way
to find out if the declaration of the Var is scoped lexicalref or not.

Unfortunately, finding the Var in the Block's first Stmts is sometimes
a bit of work.

This reverts commit 80bf3d003c1c464ac8663e86d9f8d93423e0a51e.

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