AUI-981 node.get('children') returns comments in IE6-8

Hey @eduardolundgren

This is a patch that will fix a lot of bugs in IE8 and below. As of now in trunk, anywhere where tabview is used (including all instances of form navigator), the tabs will not direct to the right content. The issue is that node.get('children') in IE8 and below will return comments in the html as children.

GetChildren will usually just return the result of node.children, which is what returns the comments in IE. So this fix forces getChildren to loop through the childNodes, filtering out anything other than html elements (childNodes[i].nodeType === 1), which is what node.children is supposed to return.

There is currently a ticket reported for this issue in yui, but it hasn't been touched in a year now, and with the upcoming release this patch would save us from having a lot of IE bugs reported. Let me know if you have any questions!