[dom] Add EventListenerOptions (#82)

My first crack at incorporating the ideas and discussion from my [EventListenerOptions proposal](https://github.com/RByers/EventListenerOptions) into the spec.  The result can be previewed [here](https://rawgit.com/RByers/dom/event-listener-options/dom.html).

One thing I'm still not super happy with is the somewhat confusing defaults for `mayCancel`.  On the one hand we [agreed](https://github.com/RByers/EventListenerOptions/issues/17) that we wanted the performance behavior (`mayCancel:false`) the be the default when using the new API form.  But we of course can't [change the existing behavior](https://github.com/RByers/EventListenerOptions/issues/22).  Let's discuss that further [here](https://github.com/RByers/EventListenerOptions/issues/17) if desired.

You can view, comment on, or merge this pull request online at:

  https://github.com/whatwg/dom/pull/82

-- Commit Summary --

  * Add EventListenerOptions

-- File Changes --

    M dom.bs (130)
    M dom.html (159)

-- Patch Links --

https://github.com/whatwg/dom/pull/82.patch
https://github.com/whatwg/dom/pull/82.diff

---
Reply to this email directly or view it on GitHub:
https://github.com/whatwg/dom/pull/82