Update directory-files{,-recur} argument checking

Update directory-files{,-recur} argument checking

       * dired.c(Fdirectory_files): Ensure directory is a string.
       (Fdirectory_files_recur): Remove check for match. It is done in
       directory_files_magic, which also will allow for a predicate.

Signed-off-by: Nelson Ferreira <nelson.ferreira@ieee.org>