Bump 4.0 branch to version 4.0.21.

Built from https://develop.svn.wordpress.org/branches/4.0@42325


git-svn-id: http://core.svn.wordpress.org/branches/4.0@42154 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/about.php

@@ -42,7 +42,11 @@ include( ABSPATH . 'wp-admin/admin-header.php' );
 </h2>
 
 <div class="changelog point-releases">
-	<h3><?php echo _n( 'Maintenance and Security Release', 'Maintenance and Security Releases', 20 ); ?></h3>
+	<h3><?php echo _n( 'Maintenance and Security Release', 'Maintenance and Security Releases', 21 ); ?></h3>
+	<p><?php printf( _n( '<strong>Version %1$s</strong> addressed a security issue.',
+			'<strong>Version %1$s</strong> addressed some security issues.', 4 ), '4.0.21' ); ?>
+		<?php printf( __( 'For more information, see <a href="%s">the release notes</a>.' ), 'https://codex.wordpress.org/Version_4.0.21' ); ?>
+	</p>
 	<p><?php printf( __( '<strong>Version %s</strong> addressed one security issue.' ), '4.0.20' ); ?>
 		<?php printf( __( 'For more information, see <a href="%s">the release notes</a>.' ), 'https://codex.wordpress.org/Version_4.0.20' ); ?>
 	</p>

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.0.20';
+$wp_version = '4.0.21';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.