Docs: Add missing `@since` entry for `Walker::unset_children()`.

Props chiragpatel.
Fixes #39506.
Built from https://develop.svn.wordpress.org/trunk@39741


git-svn-id: http://core.svn.wordpress.org/trunk@39681 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-walker.php

@@ -404,6 +404,8 @@ class Walker {
 	/**
 	 * Unset all the children for a given top level element.
 	 *
+	 * @since 2.7.0
+	 *
 	 * @param object $e
 	 * @param array $children_elements
 	 */

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.8-alpha-39740';
+$wp_version = '4.8-alpha-39741';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.