Correctly detect URLs surrounded by parentheses in comments

* lisp/thingatpt.el (thing-at-point--bounds-of-well-formed-url):
Make parentheses match work inside comments.

* test/lisp/thingatpt-tests.el (thing-at-point-url-in-comment): Add
unit test.

lisp/thingatpt.el

@@ -380,7 +380,9 @@ the bounds of a possible ill-formed URI (one lacking a scheme)."
 	     (save-restriction
 	       (narrow-to-region (1- url-beg) (min end (point-max)))
 	       (setq paren-end (ignore-errors
-				 (scan-lists (1- url-beg) 1 0))))
+                                 ;; Make the scan work inside comments.
+                                 (let ((parse-sexp-ignore-comments nil))
+                                   (scan-lists (1- url-beg) 1 0)))))
 	     (not (blink-matching-check-mismatch (1- url-beg) paren-end))
 	     (setq end (1- paren-end)))
 	;; Ensure PT is actually within BOUNDARY. Check the following

test/lisp/thingatpt-tests.el

@@ -120,4 +120,13 @@ position to retrieve THING.")
         (should (equal (list-at-point)
                        (cdr str-res)))))))
 
+(ert-deftest thing-at-point-url-in-comment ()
+  (with-temp-buffer
+    (c-mode)
+    (insert "/* (http://foo/bar)\n(http://foo/bar(baz)) */\n")
+    (goto-char 6)
+    (should (equal (thing-at-point 'url) "http://foo/bar"))
+    (goto-char 23)
+    (should (equal (thing-at-point 'url) "http://foo/bar(baz)"))))
+
 ;;; thingatpt.el ends here