Handle prompt rules of ksh in OpenBSD 4.5. Reported by Raphaël

Handle prompt rules of ksh in OpenBSD 4.5.  Reported by Raphaël
Berbain <raphael.berbain@gmail.com>.

* net/tramp.el (tramp-end-of-output): Move up.  Use `#' and `$'
characters.
(tramp-initial-end-of-output): New defconst.
(tramp-methods, tramp-find-shell)
(tramp-open-connection-setup-interactive-shell)
(tramp-maybe-open-connection): Use it.
(tramp-shell-prompt-pattern, tramp-wait-for-output): Handle
existence of `#' and `$'.

* net/tramp-fish.el (tramp-fish-maybe-open-connection): Use
`tramp-initial-end-of-output'.