[generator] use libxml internal errors

printing huuuuge warning stack traces to stdout is unhelpful

Author: shish

generator/src/XmlDocParser/DocPage.php

@@ -126,6 +126,7 @@ public function loadAndResolveFile(): \SimpleXMLElement
             .'<!DOCTYPE refentry SYSTEM "'.$path.'">'
             .\substr($content, $strpos+1);
 
+        libxml_use_internal_errors(true);
         $elem = \simplexml_load_string($content, \SimpleXMLElement::class, LIBXML_DTDLOAD | LIBXML_NOENT);
         if ($elem === false) {
             throw new \RuntimeException('Invalid XML file for '.$this->path);