check_and_publish_future_post() doesn't check that timestamp is in the past

[markjaquith]

check_and_publish_future_post() is the function that is called for future-published posts. It guards against drafts being published, but it doesn't make sure that the publish date of the post is in the past. This can lead to posts being published early, if an earlier WP-Cron entry wasn't properly cleared out.

Giving this a high priority, as this could lead to embarrassing early postings.

Also, if it attempts to publish itself early, we should make sure that the correct scheduled event is set so it doesn't get stuck as "Scheduled" forever.

[markjaquith]

(In [9123]) Prevent future posts from publishing early. fixes #7441