This patch adds the EventTarget class and makes Node inherit from it.
You can register event listeners on an EventTarget, and when you call
dispatch_event() on it, the event listeners will get invoked.
An event listener is basically a wrapper around a JS::Function*.
This is pretty far from how DOM events should eventually work, but it's
a place to start and we'll build more on top of this. :^)
This patch introduces the Wrapper and Wrappable classes.
Node now inherits from Wrappable, and can be wrapped in a GC-allocated
Bindings::NodeWrapper object. The only property we expose right now is
the very simple nodeName property.
When a Document's JS::Interpreter is first instantiated, we add a
"document" property with a DocumentWrapper object to the global object.
This is pretty cool! :^)
