When using `meta_query` in a `WP_Query`, passing `NOT EXISTS` or `''` to `compare` should not require `value` to be set. The resulting SQL should then produce the appropriate `OR` clause for existence of non-existence after passing the query to the `$key_only_queries` stack internally.

Adds unit tests. 

Props chrisguitarguy, for the original patch.
Fixes #23268.



git-svn-id: https://develop.svn.wordpress.org/trunk@27689 602fd350-edb4-49c9-b593-d223f7449a82
In `wp_create_post_autosave()`, intersect the `$new_autosave`'s keys with the keys from `_wp_post_revision_fields()` to ensure that all expected fields are present.

Props kovshenin.
Fixes #25416.



git-svn-id: https://develop.svn.wordpress.org/trunk@27690 602fd350-edb4-49c9-b593-d223f7449a82
RSS widgets: Omit the title attribute when the summary is shown.

Trim the title attribute to ensure whitespace isn't rendered.

props SergeyBiryukov.
fixes #26520. see #26552.


git-svn-id: https://develop.svn.wordpress.org/trunk@27691 602fd350-edb4-49c9-b593-d223f7449a82
Use the current post's post type when determining post adjacency.

props ethitter.
fixes #26937.


git-svn-id: https://develop.svn.wordpress.org/trunk@27692 602fd350-edb4-49c9-b593-d223f7449a82
Let us pass `jshint:core`.



git-svn-id: https://develop.svn.wordpress.org/trunk@27693 602fd350-edb4-49c9-b593-d223f7449a82