Minor EDN cleanup. (#217) r=jsantell
Minor EDN cleanup. (#217) r=jsantell

* to_reverse -> to_reversed.
* Add PlainSymbol::plain_name for examining $x and ?y.
* Fix comment.

mozilla/mentat,ncalexan/datomish,ncalexan/mentat,mozilla/mentat,mozilla/mentat,mozilla/mentat,mozilla/mentat,ncalexan/mentat,ncalexan/mentat,ncalexan/mentat,ncalexan/datomish,ncalexan/mentat,mozilla/mentat,ncalexan/mentat