Add user parameter to differential.createrevision

Summary: arc incorrectly passes a "user" parameter to differential.createrevision (long ago, we respected it, I think). After D4191 this fatals. Provide a stub call until the next version bump.

Test Plan: inspection

Reviewers: vrana, btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D4220

src/applications/conduit/method/differential/ConduitAPI_differential_createrevision_Method.php

@@ -12,6 +12,9 @@ final class ConduitAPI_differential_createrevision_Method
 
   public function defineParamTypes() {
     return array(
+      // TODO: Arcanist passes this; prevent fatals after D4191 until Conduit
+      // version 7 or newer.
+      'user'   => 'ignored',
       'diffid' => 'required diffid',
       'fields' => 'required dict',
     );