RemoteFileNameCharset is a fine-tuning command for indexing the
usually for FTP sites, when the sites have national letters in directory
and file names.
By default, directory and file names (after %XX URL-unescaping) considered to have the same character set with the character set specified in RemoteCharset. RemoteFileNameCharset allows to set an alternative character set for directory and file names, different from RemoteCharset.