PHT's for Differential.

Summary:
Went through this last night, I had to remove some static vars, but didn't see that as a huge perf issue.

Lint

Test Plan: Tested numerous differential pages, creating a diff, commenting, editing.

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4617

src/applications/differential/controller/DifferentialChangesetViewController.php

@@ -252,7 +252,7 @@ final class DifferentialChangesetViewController extends DifferentialController {
         $panel
       ),
       array(
-        'title' => 'Changeset View',
+        'title' => pht('Changeset View'),
       ));
   }