Add wp_json_encode(), a wrapper for json_encode() that ensures everything is converted to UTF-8.

Change all core calls from `json_encode()` to `wp_json_encode()`.

Fixes #28786.



git-svn-id: https://develop.svn.wordpress.org/trunk@30055 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/template.php

@@ -1952,7 +1952,7 @@ final class WP_Internal_Pointers {
 		<script type="text/javascript">
 		//<![CDATA[
 		(function($){
-			var options = <?php echo json_encode( $args ); ?>, setup;
+			var options = <?php echo wp_json_encode( $args ); ?>, setup;
 
 			if ( ! options )
 				return;