Cache: add option to delete file from permissions cache for all users

lib/files/cache/permissions.php

@@ -91,10 +91,15 @@ class Permissions {
 	 * @param int $fileId
 	 * @param string $user
 	 */
-	public function remove($fileId, $user) {
+	public function remove($fileId, $user = null) {
+		if (is_null($user)) {
+			$query = \OC_DB::prepare('DELETE FROM `*PREFIX*permissions` WHERE `fileid` = ?');
+			$query->execute(array($fileId));
+		} else {
 			$query = \OC_DB::prepare('DELETE FROM `*PREFIX*permissions` WHERE `fileid` = ? AND `user` = ?');
 			$query->execute(array($fileId, $user));
 		}
+	}
 
 	public function removeMultiple($fileIds, $user) {
 		$query = \OC_DB::prepare('DELETE FROM `*PREFIX*permissions` WHERE `fileid` = ? AND `user` = ?');