ftpserver.pl: directory LISTings use [CR][LF] for ASCII transfer

According to section 2.2 of RFC959 the End-of-Line is defined as:
 The end-of-line sequence defines the separation of printing
 lines.  The sequence is Carriage Return, followed by Line Feed.

Verified by sniffing traffic between a Windows FTP client (FileZilla)
and Unix-hosted FTP server (ProFTPD).