Mark ext/xmlreader/tests/bug70309.phpt as online test

The relax NG schema is fetched from a remote server. We could
include it in the repo, but it's 500KB. A minimized test case would
be better.

Also, apparently this bug has never been reported upstream and just
patched in the libxml we build on Windows?

Author: nikic

ext/xmlreader/tests/bug70309.phpt

@@ -4,6 +4,7 @@ XMLReader: Bug #70309 XmlReader read generates extra output
 <?php if (substr(PHP_OS, 0, 3) != 'WIN') die('skip.. only for Windows'); ?>
 <?php if (!extension_loaded("xmlreader")) print "skip"; ?>
 <?php if (getenv("SKIP_SLOW_TESTS")) die("skip slow test"); ?>
+<?php if (getenv("SKIP_ONLINE_TESTS")) die("skip online test"); ?>
 --FILE--
 <?php