[ticket/12522] Add function parameter description in guesser interface

Add parameter description for $file_name of the function guess in
guesser_interface

PHPBB3-12522
Merge pull request #2435 from n-aleha/ticket/12522

[ticket/12522] Add function parameter description in guesser interface

* n-aleha/ticket/12522:
  [ticket/12522] Add function parameter description in guesser interface