Make get_adjacent_post() wrap a new WP_Get_Adjacent_Post object that uses WP_Query.

See [27285] for the actual commit, which misfired.

props ethitter!
fixes #26937.


git-svn-id: https://develop.svn.wordpress.org/trunk@27286 602fd350-edb4-49c9-b593-d223f7449a82
We shall call it WP_Adjacent_Post instead. see #26937.


git-svn-id: https://develop.svn.wordpress.org/trunk@27287 602fd350-edb4-49c9-b593-d223f7449a82
One more change. see #26937.


git-svn-id: https://develop.svn.wordpress.org/trunk@27288 602fd350-edb4-49c9-b593-d223f7449a82