[ticket/16287] After installation an error is given over statistics submission

The phpBB.com website required specific fields to be available for the
statistics. This change switched over to a new statistics page on
www.phpbb.com that uses form fields instead, and that returns JSON as value.

PHPBB3-16287

phpBB/adm/style/ajax.js

@@ -1,4 +1,4 @@
-/* global phpbb */
+/* global phpbb, statsData */
 
 (function($) {  // Avoid conflicts with other libraries
 
@@ -87,7 +87,7 @@ phpbb.prepareSendStats = function () {
 		$.ajax({
 			url: $this.attr('data-ajax-action').replace('&', '&'),
 			type: 'POST',
-			data: 'systemdata=' + encodeURIComponent($this.find('input[name=systemdata]').val()),
+			data: statsData,
 			success: returnHandler,
 			error: errorHandler,
 			cache: false