Tilde in URL breaks things

A tilde (~) in a URL makes the BBCode module fail to parse it properly. For example, http://www.example.com/~dir/sample.html will not be automaticly converted to a URL, and [img]http://www.example.com/~dir/sample.jpg[/img] will be displayed as entered in text, rather than being converted to a proper <img /> tag.

There may be other valid URL characters that don't work, this is just the one I've noticed.