fenner 02979f47f2 Teach ftpErrString to format UNIX errnos, since at least ftpLogin()
can return UNIX errnos.  When UNIX errnos catch up with FTP status
codes (e.g. at 100) a new way will have to be found to tell which
is which.

This allows fetch to print errors like
fetch: ftp.fu-berlin.de: No route to host
instead of
fetch: ftp.fu-berlin.de: Unknown error
1997-10-02 23:26:03 +00:00
..
1997-02-22 15:12:41 +00:00
1997-05-05 11:18:55 +00:00