JSONP: Add status code as callback parameter

[OliverJAsh]

Currently there is no way to communicate the request status code when using JSONP. One convention is to pass this to the callback (as the script itself must return 200 to be executed).

reqwest_1433343994338({"status":"error","errors":[{"message":"Access Denied","description":"Access Denied"}]}, 403)

Could we add this?