MDL-60424 webservice: Allow CORS requests in webservice/upload.php

This will allow to upload files via Web Services using AJAX from
different domains, browser plugins, web apps, etc…

webservice/upload.php

@@ -43,6 +43,10 @@ define('NO_MOODLE_COOKIES', true);
 
 require_once(__DIR__ . '/../config.php');
 require_once($CFG->dirroot . '/webservice/lib.php');
+
+// Allow CORS requests.
+header('Access-Control-Allow-Origin: *');
+
 $filepath = optional_param('filepath', '/', PARAM_PATH);
 $itemid = optional_param('itemid', 0, PARAM_INT);