Docs: Add a valid return type for `post_preview()` and improve the DocBlock summary.

See #41017.

Built from https://develop.svn.wordpress.org/trunk@40985


git-svn-id: http://core.svn.wordpress.org/trunk@40835 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/post.php

@@ -1722,12 +1722,12 @@ function wp_create_post_autosave( $post_data ) {
 }
 
 /**
- * Save draft or manually autosave for showing preview.
+ * Saves a draft or manually autosaves for the purpose of showing a post preview.
  *
  * @package WordPress
  * @since 2.7.0
  *
- * @return str URL to redirect to show the preview
+ * @return string URL to redirect to show the preview.
  */
 function post_preview() {
 

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.9-alpha-40984';
+$wp_version = '4.9-alpha-40985';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.