update changelog

CHANGELOG.md

@@ -5,8 +5,11 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased] - ReleaseDate
 ### Added
-- Add `CLK_TCK` to `SysconfVar`
+- Added `CLK_TCK` to `SysconfVar`
   (#[1177](https://github.com/nix-rust/nix/pull/1177))
+
+- Added `unistd::setfsuid` and `unistd::setfsgid` to set the user or group
+    identity for filesystem checks per-thread.
 ### Changed
 ### Fixed
 ### Removed