Upgrade Backbone to 1.1.2

[gcorne]

Backbone 1.1.1 and 1.1.2 have both been released. We should upgrade.

Changelog for 1.1.2:

• Backbone no longer tries to require jQuery in Node/CommonJS environments, for better compatibility with folks using Browserify. If you'd like to have Backbone use jQuery from Node, assign it like so: Backbone.$ = require('jquery');
• Bugfix for route parameters with newlines in them.

Change log for 1.1.1:

• Backbone now registers itself for AMD (Require.js), Bower and Component, as well as being a CommonJS module and a regular (Java)Script. Whew.
• Added an execute hook to the Router, which allows you to hook in and custom-parse route arguments, like query strings, for example.
• Performance fine-tuning for Backbone Events.
• Better matching for Unicode in routes, in old browsers.

In particular, the addition of an execute hook may help us with #26543

[gcorne]

27182-01.patch​ takes care of the upgrade.

[gcorne]

27182-02.patch​ adds backbone.min.js back, which was accidentally left out.

[ocean90]

Fixed in [27233].

I have removed sourceMappingURL from the minified version, see #24994 for jQuery.