minor typo

dtool/src/dtoolutil/filename.cxx

@@ -1756,7 +1756,7 @@ scan_directory(vector_string &contents) const {
   return scan_ok;
 
 #elif defined(PHAVE_DIRENT_H)
-  // Use Posix's opendir() / readir() to walk through the list of
+  // Use Posix's opendir() / readdir() to walk through the list of
   // files in a directory.
   size_t orig_size = contents.size();