Added a default detection order for mb_detect_encoding.

This ensures that at least the result will be predictable.

src/phpDocumentor/Reflection/File.php

@@ -191,7 +191,7 @@ protected function convertToUtf8($filename, $contents)
             && function_exists('mb_detect_encoding')
         ) {
             // OR with mbstring
-            $encoding = mb_detect_encoding($contents);
+            $encoding = mb_detect_encoding($contents,'UTF-8,ISO-8859-1');
         }
 
         // if the encoding is detected as binary we try again