When blog_public only has two values (as judged by whether the blog_privacy_selector action is used), convert from radio buttons to a checkbox, and rename from 'Site Visibility' to a more specific 'Search Engine Visibility'.
The text and implementation may change a bit. see #16416.
git-svn-id: https://develop.svn.wordpress.org/trunk@21838 602fd350-edb4-49c9-b593-d223f7449a82