Include extension name for GDSetupCheck.

Summary: Help for GD SetupChcek was missing the "how to install extension" content.

Test Plan: Uninstalled gd, validated extension installation instructions were present in Setup Issue.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D18922

src/applications/config/check/PhabricatorGDSetupCheck.php

@@ -18,7 +18,8 @@ final class PhabricatorGDSetupCheck extends PhabricatorSetupCheck {
 
       $this->newIssue('extension.gd')
         ->setName(pht("Missing '%s' Extension", 'gd'))
-        ->setMessage($message);
+        ->setMessage($message)
+        ->addPHPExtension('gd');
     } else {
       $image_type_map = array(
         'imagecreatefrompng'  => 'PNG',