Use `require_once()` to prevent a fatal error if `_wp_admin_bar_init()` is called twice.

props danielbachhuber.
fixes #31287.
Built from https://develop.svn.wordpress.org/trunk@31411


git-svn-id: http://core.svn.wordpress.org/trunk@31392 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/admin-bar.php

@@ -22,7 +22,7 @@ function _wp_admin_bar_init() {
 		return false;
 
 	/* Load the admin bar class code ready for instantiation */
-	require( ABSPATH . WPINC . '/class-wp-admin-bar.php' );
+	require_once( ABSPATH . WPINC . '/class-wp-admin-bar.php' );
 
 	/* Instantiate the admin bar */
 

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.2-alpha-31409';
+$wp_version = '4.2-alpha-31411';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.