(ido-enable-tramp-completion): New defcustom.

(ido-enable-tramp-completion): New defcustom.
(ido-enter-single-matching-directory): Change default to 'slash.
(ido-is-tramp-root): New defun.
(ido-is-root-directory, ido-is-ftp-directory, ido-is-slow-ftp-host)
(ido-may-cache-directory, ido-final-slash, ido-read-internal)
(ido-complete, ido-make-file-list1, ido-make-dir-list1):
Handle tramp completion.
(ido-file-name-all-completions1): New defun for tramp completion.
(ido-file-name-all-completions): Use it.
(ido-set-matches1): Relax matching of text with trailing slash.
(ido-exhibit): Handle tramp completion.
Simplified code using nested cond forms using new `refresh' var.
Fixed handling of /~user/ paths.