Use PhutilNumber instead of number_format()

Summary: Also convert to `phutil_tag()`.

Test Plan: Displayed revision with hidden comments.

Reviewers: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4772

src/applications/differential/view/DifferentialRevisionCommentListView.php

@@ -171,8 +171,9 @@ final class DifferentialRevisionCommentListView extends AphrontView {
           ),
           array(
             pht(
-              '%d older comments are hidden. ',
+              '%s older comments are hidden.',
-              number_format(count($hidden))),
+              new PhutilNumber(count($hidden))),
+            ' ',
             javelin_tag(
               'a',
               array(