RemoteFileNameCharset is a fine-tuning command for indexing the
url.file and url.path sections,
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.