[zendframework#293] Make new method public

- Since it's being invoked as a static callback, the method needs to be
  public. Renamed to remove the underscore prefix, and marked as public.

Xml/Security.php

@@ -51,7 +51,7 @@ protected static function heuristicScan($xml)
      * @param integer $errline
      * @return bool
      */
-    protected static function _loadXmlErrorHandler($errno, $errstr, $errfile, $errline)
+    public static function loadXmlErrorHandler($errno, $errstr, $errfile, $errline)
     {
         if (substr_count($errstr, 'DOMDocument::loadXML()') > 0) {
             return true;
@@ -88,7 +88,7 @@ public static function scan($xml, DOMDocument $dom = null)
 
         // Load XML with network access disabled (LIBXML_NONET)
         // error disabled with @ for PHP-FPM scenario
-        set_error_handler(array('Zend_Xml_Security', '_loadXmlErrorHandler'), E_WARNING);
+        set_error_handler(array('Zend_Xml_Security', 'loadXmlErrorHandler'), E_WARNING);
 
         $result = $dom->loadXml($xml, LIBXML_NONET);
         restore_error_handler();