Backport commit 93fe42094 from Emacs

This follows on a suggestion by Stefan Monnier in:
https://lists.gnu.org/r/emacs-devel/2018-08/msg00991.html
(Bug#32902).

* lisp/org-id.el (org-id-uuid, org-id-time-to-b36):
Don't assume timestamps default to list form.

New (TICKS . HZ) timestamp format
93fe420942c08111a6048af7c4d7807c61d80a09
Paul Eggert
Sat Oct 6 23:31:04 2018 -0700

lisp/org-id.el

@@ -358,7 +358,7 @@ So a typical ID could look like \"Org:4nd91V40HI\"."
   "Return string with random (version 4) UUID."
   (let ((rnd (md5 (format "%s%s%s%s%s%s%s"
 			  (random)
-			  (current-time)
+			  (encode-time nil 'list)
 			  (user-uid)
 			  (emacs-pid)
 			  (user-full-name)
@@ -417,7 +417,7 @@ The input I may be a character, or a single-letter string."
   "Encode TIME as a 10-digit string.
 This string holds the time to micro-second accuracy, and can be decoded
 using `org-id-decode'."
-  (setq time (or time (current-time)))
+  (setq time (encode-time time 'list))
   (concat (org-id-int-to-b36 (nth 0 time) 4)
 	  (org-id-int-to-b36 (nth 1 time) 4)
 	  (org-id-int-to-b36 (or (nth 2 time) 0) 4)))