Implement `defprotocol` and `deftype`

[ingydotnet]

slipset: WRT the persistent data structures. In Clojure they were implemented in Java, and based on Java interfaces. In Clojurescript, they’re all implemented in Clojure and based on protocols. I think the latter is preferable. One would then end up in a world where Perl was missing an implementation of persistent data structures, but that could be addressed in other ways :)

hifumi123: to fast track lingy, we will want to get deftype and defprotocol nailed down first, and then we can take most of CLJS' implementation of clojure.core