Avoid PHP notices in _count_posts_cache_key(), _update_blog_date_on_post_publish(), and _update_blog_date_on_post_delete() if post type is not registered.

props jesin.
fixes #28135.
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git-svn-id: http://core.svn.wordpress.org/trunk@29099 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Use 3-digit x.x.x style for two 4.0.0 @since versions.

see #28885.
Built from https://develop.svn.wordpress.org/trunk@29319


git-svn-id: http://core.svn.wordpress.org/trunk@29100 1a063a9b-81f0-0310-95a4-ce76da25c4cd