colons not handled in urls

The BBcode module doesn't include any text after a ":" in a url string that is within [url=abc] tags.

Here's an example:
http://en.wikibooks.org/wiki/Transwiki:How_to_learn_a_language

That gets cut down to:
http://en.wikibooks.org/wiki/Transwiki

One option, as a middle step, is to allow users to optionally use quotation marks in the bbcode url tags to specify the whole url. (This is probably a good idea anyway, even if the bug is fixed some other way. This way, users who are used to using quote marks in href's aren't too inconvenienced.)