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/customize.php

@@ -274,7 +274,7 @@ do_action( 'customize_controls_print_scripts' );
 
 	?>
 	<script type="text/javascript">
-		var _wpCustomizeSettings = <?php echo json_encode( $settings ); ?>;
+		var _wpCustomizeSettings = <?php echo wp_json_encode( $settings ); ?>;
 	</script>
 </div>
 </body>