(Arcanist wilds) Add setHint/getHint to PhutilLockException for recent lock changes

Summary: Ref T13202. See PHI889. See D19702. A small part of that change affected libphutil, but got lost in the shuffle with all the Arcanist/wilds stuff in my local workspace.

Test Plan: See D19702.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13202

Differential Revision: https://secure.phabricator.com/D19720

src/filesystem/PhutilLockException.php

@@ -1,3 +1,16 @@
 <?php
 
-final class PhutilLockException extends Exception {}
+final class PhutilLockException extends Exception {
+
+  private $hint;
+
+  public function setHint($hint) {
+    $this->hint = $hint;
+    return $this;
+  }
+
+  public function getHint() {
+    return $this->hint;
+  }
+
+}