Fix coercion of optional parameters
Fix coercion of optional parameters

A `Target(Constraint)` typed optional parameter must have it's default
set to `Constraint`.

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