Update addon-PrefixForumListing.xml

And a last modification to allow visual customization of the prefixes box (I had a margin problem with the reply button), the main phrase, the item (the previous fix of 7px for multilines has been moved here) and counter.
These customization can be configure from the XenForo visual options
You should try it first and see everything is ok for you :)
Have a nice day !
Merge pull request #2 from cclaerhout/patch-2

Update addon-PrefixForumListing.xml