IE Leak: Array.flatten

[ibolmo]

As per: #2127 (comment)

It appears that the calling of instanceof on 'non-objects' (mootools.js flatten()) causes the memory leaks in IE. http://ajaxian.com/archives/working-aroung-the-instanceof-memory-leak

We ended up implementing the following:

if(Browser.ie) {
        instanceOf = this.instanceOf = function(item, object) {
            if (item == null) return false;
            // Avoid calling instanceof on certain "non-objects" to prevent memory leaks in IE
            if (!item.hasOwnProperty) return false;
            var constructor = item.$constructor || item.constructor;
            while (constructor){
                if (constructor === object) return true;
                constructor = constructor.parent;
            }
            return item instanceof object;
        };
    }