Improve XEmacs compatibility of Tramp
* lisp/net/tramp-compat.el (directory-listing-before-filename-regexp):
Declare if it doesn't exist.
(file-remote-p): Remove defalias, which was necessary for GNU Emacs 21.
(redisplay): Make it an alias if it doesn't exist.
* lisp/net/tramp.el (tramp-get-remote-tmpdir): Don't use
`file-remote-p' (due to XEmacs compatibility).
* lisp/net/trampver.el (locate-dominating-file)
(tramp-compat-replace-regexp-in-string): Autoload.
(tramp-repository-get-version): Do not dupe byte-compiler.