Replace array_interleave() by phutil_implode_html()

Summary:
I like this abstraction better.
Result of `phutil_implode_html()` may be also used as a param of `hsprintf()`.

Test Plan: None.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4904

src/applications/base/controller/PhabricatorController.php

@@ -277,7 +277,7 @@ abstract class PhabricatorController extends AphrontController {
       $items[] = $this->getHandle($phid)->renderLink();
     }
 
-    return array_interleave($style_map[$style], $items);
+    return phutil_implode_html($style_map[$style], $items);
   }
 
   protected function buildApplicationMenu() {