Posts, Post Types: Introduce a missing private query var that should have been introduced as part of #15459.

This private query var allows the hierarchical page query on the Pages listing screen to query for `wp_posts.ID, wp_posts.post_parent` instead of `wp_posts.*`. This introduces large memory and time savings when the site contains a large number of Pages. Combined with the processing time savings introduced in [31730] this makes the Pages listing screen considerably more performant.

Fixes #34982
Props rodrigosprimo

Built from https://develop.svn.wordpress.org/trunk@38451


git-svn-id: http://core.svn.wordpress.org/trunk@38392 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp.php

@@ -26,7 +26,7 @@ class WP {
 	 * @access public
 	 * @var array
 	 */
-	public $private_query_vars = array( 'offset', 'posts_per_page', 'posts_per_archive_page', 'showposts', 'nopaging', 'post_type', 'post_status', 'category__in', 'category__not_in', 'category__and', 'tag__in', 'tag__not_in', 'tag__and', 'tag_slug__in', 'tag_slug__and', 'tag_id', 'post_mime_type', 'perm', 'comments_per_page', 'post__in', 'post__not_in', 'post_parent', 'post_parent__in', 'post_parent__not_in', 'title' );
+	public $private_query_vars = array( 'offset', 'posts_per_page', 'posts_per_archive_page', 'showposts', 'nopaging', 'post_type', 'post_status', 'category__in', 'category__not_in', 'category__and', 'tag__in', 'tag__not_in', 'tag__and', 'tag_slug__in', 'tag_slug__and', 'tag_id', 'post_mime_type', 'perm', 'comments_per_page', 'post__in', 'post__not_in', 'post_parent', 'post_parent__in', 'post_parent__not_in', 'title', 'fields' );
 
 	/**
 	 * Extra query variables set by the user.

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.7-alpha-38450';
+$wp_version = '4.7-alpha-38451';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.