(rlogin-initially-track-cwd): New variable.

(rlogin-initially-track-cwd): New variable.
(rlogin): Use it to determine whether enable directory tracking
via ange-ftp.
(rlogin-mode): Make `comint-filename-prefix' local here.

(rlogin): Arguments to function are now a string with
multiple words (hostname first) and an optional prefix.
(rlogin-with-args): Function deleted.

(rlogin): Set process filter after calling
`rlogin-mode' since the latter called `comint-mode', which sets
its own initial process filter.