utop.el: Fix utop-tuareg-next-phrase for newer tuareg.el

tuareg--after-double-colon no longer exists in the latest rev of
Tuareg, which has received 110 additional commits since the last
release version on OPAM, so inline the old definition, which was
removed in commit 91ba1d6143558092a3920e9b5c49755c0c86caed of Tuareg.

tuareg--skip-double-colon was renamed to
tuareg--skip-double-semicolon, and also received a slight change.
Inline that as well since it's a private function.

src/top/utop.el

@@ -5,7 +5,7 @@
 ;; URL: https://github.com/diml/utop
 ;; Licence: BSD3
 ;; Version: 1.11
-;; Package-Requires: ((emacs "24"))
+;; Package-Requires: ((emacs "24") (tuareg "2.2.0"))
 ;; Keywords: ocaml languages
 
 ;; This file is a part of utop.
@@ -20,6 +20,7 @@
 (require 'easymenu)
 (require 'pcase)
 (require 'tabulated-list)
+(require 'tuareg)
 
 ;; +-----------------------------------------------------------------+
 ;; | License                                                         |
@@ -269,12 +270,18 @@ modes you need to set these variables:
 
 (defun utop-tuareg-next-phrase ()
   "Move to the next phrase after point."
-  (let* ((pos (tuareg--after-double-colon))
+  (let* ((pos (save-excursion
+                (when (looking-at-p "[;[:blank:]]*$")
+                  (skip-chars-backward ";[:blank:]")
+                  (when (> (point) 1)
+                    (- (point) 1)))))
          (pos (if pos pos (point)))
          (phrase (tuareg-discover-phrase pos)))
     (when phrase
       (goto-char (caddr phrase))
-      (tuareg--skip-double-colon)
+      (tuareg-skip-blank-and-comments)
+      (when (looking-at ";;[ \t\n]*")
+        (goto-char (match-end 0)))
       (tuareg-skip-blank-and-comments))))
 
 (defun utop-compat-next-phrase-beginning ()