Switch in and out of PHP to render fallback title.

The upload checks for the .org Theme Directory are rightfully strict about the contents of the title tag.
Switching in and out of PHP should make `_s`-based themes pass those tests again.

See https://github.com/Automattic/_s/pull/644#discussion-diff-22153263
See #644.

inc/extras.php

@@ -77,7 +77,9 @@ if ( ! function_exists( '_wp_render_title_tag' ) ) :
 	 * @todo Remove this function when WordPress 4.3 is released.
 	 */
 	function _s_render_title() {
-		echo '<title>' . wp_title( '|', false, 'right' ) . "</title>\n";
+		?>
+		<title><?php wp_title( '|', true, 'right' ); ?></title>
+		<?php
 	}
 	add_action( 'wp_head', '_s_render_title' );
 endif;