Replace vertical tabs befor parsing XML in XMLRPC

It seems that the 0x0B Vertical Tab character breaks the PHP
XML parser. This workaround replaces the char with a space
before parsing. Not ideal but good enough for now.

inc/IXR_Library.php

@@ -150,6 +150,7 @@ class IXR_Message {
         $this->message = str_replace('&', '&', $this->message);
         $this->message = str_replace(''', ''', $this->message);
         $this->message = str_replace('"', '"', $this->message);
+        $this->message = str_replace("\x0b", ' ', $this->message); //vertical tab
         if (trim($this->message) == '') {
             return false;
         }