Tweaked [7082] and [7084] a little bit to also allow comment nodes prior to the extends tag.

This would be little less fiddly if we knew nodelist were always of type
NodeList, but they could be normal lists. Or if we merged successive TextNodes,
instead of appending them. Something to think about going forwards.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@7089 bcc190cf-cafb-0310-a4f2-bffc1f526a37