Bug 1093219 - m3u parsing

I think it is hard to reliably distinguish urls from filenames, and I'm not sure this parsing function is the right place to do it. What if you just return whatever path you find.  Somewhere else you're going to have to validate those paths to see if they refer to files that you know about. So when you remove entries that refer to files you don't have you can also remove urls at that point.