Update Backbone to 0.9.10. Update media to handle breaking changes.

* When overriding `Backbone.sync()`, ensure the `sync` and `error` events fire consistently.

* `Model#make()` has been removed. Use `$` instead, and be sure to grab the DOM node where necessary (using `[0]`).

* `Collection#get()` now accepts `cid`s. `Collection#getByCid()` has been removed.

* When overriding the `State` constructor, bind `change` callbacks after the default `Model` constructor is called, because the `Model` constructor no longer passes the `silent` flag when calling `set()` for the default attributes.

* In 'change' events, `options.changes` was removed. It can now be accessed through `model.changed`. Check if any attributes have changed by calling `model.hasChanged()`. Also, don't mess with `model.changed`; it persists beyond the scope of a single event.

* `options.index` is no longer be set in the `add` event callback. Use `collection.indexOf(model)` can be used to retrieve the index of a model instead.

props gcorne. fixes #23262.


git-svn-id: https://core.svn.wordpress.org/trunk@23589 1a063a9b-81f0-0310-95a4-ce76da25c4cd