XHR2 uploads using Drupal ajax framework

I wanted to use the XMLHttpRequest level 2 capabilities which modern browsers support to create an easy way of uploading (multiple) files in Drupal. You know, the kinda way Gmail and now also Facebook do it. While this isn't that hard to use standalone (HTML5 demo here), it was quite a challenge implementing this using Drupal 7's ajax framework. Finally, with special thanks to rudiedirkx, a way to do this was found by overriding Drupal.ajax.prototype.eventResponse. See the whole solution on stackexchange.