[site:url-brief] token puts an unnecessary slash at the end

The [site:url-brief] token in Drupal 7 is supposed to print something like "mysite.com" (the URL of the site's front page, without the protocol).

Instead, it prints "mysite.com/" (with a slash at the end).

This makes it look extremely ugly in its primary use case (user registration emails and the like). It's also a regression from D6, where the equivalent user.module variable did not put the slash at the end.

The attached patch fixes it.