(bug 28840) URLs with dots break because of IE6 security check

(bug 28840) URLs with dots break because of IE6 security check

* Replace the overly paranoid regex with a function that simulates IE6's behavior
* Remove the UA check in isPathInfoBad(), was causing more problems than it was worth
* Revert r87711, going back to using dots for dots in ResourceLoader URLs, instead of exclamation marks
* Append &* to ResourceLoader URLs. * is an illegal character in extensions, and putting it at the end of the URL ensures that both IE6 and our detection function will deem the URL to have no extension (unless something like .html? appears in the query string, but in that case we're screwed no matter what)