JS iteration issue in IPE breaks IE8

The Panels IPE JavaScript code uses the for (var k in obj) ... idiom without checking hasOwnProperty. In older versions of IE, this can cause some havoc in Drupal.settings.PanelsIPECacheKeys, as some array shims can cause methods like "map" and "forEach" to appear as object keys, causing a jQuery syntax error in the line $('div#panels-ipe-display-' + key + ':not(.panels-ipe-processed)').

I've attached a patch which resolves the issue I experienced.