Twenty Twelve: Use the correct body class for attachments in the IE stylesheet.

props Marco_Teethgrinder.
see #25506. see [25707].


git-svn-id: https://develop.svn.wordpress.org/trunk@25715 602fd350-edb4-49c9-b593-d223f7449a82
Twenty Thirteen: Remove unneeded .single-attachment selector.

props obenland.
fixes #25506.


git-svn-id: https://develop.svn.wordpress.org/trunk@25716 602fd350-edb4-49c9-b593-d223f7449a82