URL regexes including non-valid addresses (catches text before valid URL as well)

Following my earlier report and fix for the URL token being made clickable (http://www.phpbb.com/bugs/phpbb3/ticket.php?ticket_id=14151) I've checked on the fix and there seems to be another issue (which may have been there all along).

Given the custom BBCode

[link]{TEXT} {URL}[/link]

which is replaced by

<a href="{URL}">{TEXT}</a>

Then the test post

[link]something else http://www.ibboard.co.uk[/link]

gives us

<a href="else%20http://www.ibboard.co.uk">something</a>

where as it should give

<a href="http://www.ibboard.co.uk">something else</a>

I've not tracked down the exact cause or a fix yet, but it seems like the regex for the

token is matching spaces in what would be the domain section of the pattern, which is incorrect behaviour.

I thought the cause might be the numerous unescaped '.' characters in the patterns in get_preg_expression() in functions.php that were matching spaces rather than literal .s, but escaping them doesn't seem to have fixed it so far.

Hopefully I'll be able to provide more useful information when I work out what the rather complex regexes are doing!