Cygwin: document recent changes

winsup/cygwin/release/3.1.3

@@ -1,5 +1,18 @@
-Bug Fixes
----------
+What changed:
+-------------
+
+- Allow symlinks to be opened with O_PATH | O_NOFOLLOW.
+
+- Allow the pathname argument to readlinkat(2) to be an empty string,
+  provided the dirfd argument refers to a symlink opened with
+  O_PATH | O_NOFOLLOW.  The readlinkat call then operates on that
+  symlink.
+
+- Support the Linux-specific AT_EMPTY_PATH flag for fchownat(2) and
+  fstatat(2).
+
+Bug Fixes:
+----------
 
 - Define CPU_SETSIZE, as on Linux.
   Addresses: https://cygwin.com/ml/cygwin/2019-12/msg00248.html
@@ -7,6 +20,6 @@ Bug Fixes
 - Fix the problem which overrides the code page setting.
   Addresses: https://www.cygwin.com/ml/cygwin/2019-12/msg00292.html
 
-- Fix a regression that prevents the root of a drive from being the
+- Fix a regression that prevented the root of a drive from being the
   Cygwin installation root.
   Addresses: https://cygwin.com/ml/cygwin/2020-01/msg00111.html