Twenty Twelve: better layout for floated image captions. Fixes #23147.

git-svn-id: http://core.svn.wordpress.org/trunk@23472 1a063a9b-81f0-0310-95a4-ce76da25c4cd
POT, generated from r23472

git-svn-id: http://core.svn.wordpress.org/trunk@23473 1a063a9b-81f0-0310-95a4-ce76da25c4cd