support for literal IPv6 addresses in URLs

I was about to add this, but I looked at ext/standard/url.c and it was a little bit cryptic to say the least. Do you Jim or anyone else want to look at it, or should I do my best and try to understand it? What we need to handle are URLs like http://[1080::8:800:200C:417A]:8080/foo for more info see RFC 2732. We only need to change the hostport parsing. If hostport starts with [ we should ignore any : coming before ]. If there's no corresponding ], give an error. We should also give an error if hostport has a character different from : after ]. Stig