Description:
------------
How do I support the following tag type?

[product=123]

This tag accepts an argument but has NO closing tag! I know this can be 
supported like this:

[product]123[/product]
or
[product=123][/product]

But I'm sure you will agree that it is much more verbose!

I have tried combinations of using: BBCODE_TYPE_SINGLE
with a "param_handling" and/or "content_handling" callback functions! It seems 
that BBCODE_TYPE_SINGLE ignores the callbacks as soon as you add the argument 
and leave out the closing tag, probably because BBCODE_TYPE_SINGLE doesn't 
usually expect additional parameters!

I think the fix should be simple; ie. check if there are additional 
paramenters/arguments in BBCODE_TYPE_SINGLE and run the callbacks!

Test script:
---------------
$bbcodes = array(
	'product' =>  array(
			'type'              =>  BBCODE_TYPE_SINGLE,
			'content_handling'  => 'bbcode_product'
		));

function bbcode_product($content, $argument)
{
	return '[PRODUCT]' . $content . ' : ' . $argument . '[/PRODUCT]';
}

$parser = bbcode_create($bbcodes);

echo bbcode_parse($parser, '[product=123]');


Expected result:
----------------
[PRODUCT]123 : [/PRODUCT]

Actual result:
--------------
[product=123]