Fix some warnings about markup engines in Audit/Diffusion inline comments

Summary:
Split from D1921.

  - DifferentialChangesetParser doesn't have this property declared.
  - We weren't providing a markup engine, which caused some warnings.
  - This would cause failures if comment caches weren't present. Currently, they always will be though unless someone has wiped them explicitly in the DB.

Test Plan: Viewed a diff with inline comments, didn't get any warnings in the log.

Reviewers: nh, vrana, btrahan

Reviewed By: btrahan

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1925

src/applications/diffusion/controller/diff/DiffusionDiffController.php

@@ -45,6 +45,8 @@ final class DiffusionDiffController extends DiffusionController {
     $parser = new DifferentialChangesetParser();
     $parser->setChangeset($changeset);
     $parser->setRenderingReference($diff_query->getRenderingReference());
+    $parser->setMarkupEngine(
+      PhabricatorMarkupEngine::newDiffusionMarkupEngine());
 
     $pquery = new DiffusionPathIDQuery(array($changeset->getFilename()));
     $ids = $pquery->loadPathIDs();

src/applications/diffusion/controller/diff/__init__.php

@@ -13,6 +13,7 @@ phutil_require_module('phabricator', 'applications/diffusion/controller/base');
 phutil_require_module('phabricator', 'applications/diffusion/query/diff/base');
 phutil_require_module('phabricator', 'applications/diffusion/query/pathid/base');
 phutil_require_module('phabricator', 'applications/diffusion/request/base');
+phutil_require_module('phabricator', 'applications/markup/engine');
 phutil_require_module('phabricator', 'applications/phid/handle/data');
 phutil_require_module('phabricator', 'infrastructure/diff/response');