Fix regex for searching for constant lists

0242577 partly fixed the detection of external constant lists referenced on Predefined Constants pages, but changing the file search regex is needed too in order to fully fix the underlying issue in case of cURL constants.

Author: kocsismate

build/gen_stub.php

@@ -5326,7 +5326,7 @@ function replacePredefinedConstants(string $targetDirectory, array $constMap, ar
 
     foreach ($it as $file) {
         $pathName = $file->getPathName();
-        if (!preg_match('/(?:[\w\.]*constants[\w\.]*|tokens).xml$/i', basename($pathName))) {
+        if (!preg_match('/(?:[\w\.]*constants[\w\._]*|tokens).xml$/i', basename($pathName))) {
             continue;
         }