The author of the original URL-matching regex warns that the pattern may
cause certain regex engines to lock up with certain input, namely patterns
that contain parentheses. It turns out SpiderMonkey is affected, but rather
than switching to the author's improved version (that is still crazy), sim-
plify the pattern a bit by removing support for nested parentheses in URLs.
Even a single pair of parentheses is extremely rare, so this is unlikely to
make a noticeable difference (other than not locking up SpiderMonkey of