Replace clearfix solution from r1010642.

The previous commit was incorrect; `overflow: visible` does not have the same clearfix effect that `auto` does. The technique in this commit achieves the clearfix without scrollbars.


git-svn-id: https://plugins.svn.wordpress.org/tagregator/trunk@1010691 b8457f37-d9ea-0310-8a92-e5e31aec5664