Removed several more gratuitous autoload cookies.

Removed several more gratuitous autoload cookies.
rlogin-initially-track-cwd: Variable deleted.

rlogin-directory-tracking-mode: New variable and function.
Default to 'local.

rlogin-host, rlogin-remote-user: New variables.
rlogin: Set them appropriately.

rlogin-mode-map: Copy shell-mode-map fully if not a list
(in lucid emacs, keymaps are opaque objects).

rlogin-tab-or-complete: New function.
Bind C-i to it.

rlogin-carriage-filter: New function.
rlogin: Add it to comint-output-filter-functions.

rlogin-parse-words: New function.

rlogin: Make buffer name "*rlogin-USER@HOST* if remote user differs from local.
Simplify initialization of local variables, using rlogin-parse-words.
Do not call comint-mode directly.
Doc fixes.