[newlib-cygwin] Document the last change

[Ken Brown]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=a9724c3904c5680890f23ce248e4b7092eeabf35

commit a9724c3904c5680890f23ce248e4b7092eeabf35
Author: Ken Brown <kbrown@cornell.edu>
Date:   Tue Sep 24 15:31:17 2019 -0400

    Document the last change

Diff:
---
 winsup/cygwin/release/3.1.0 | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/winsup/cygwin/release/3.1.0 b/winsup/cygwin/release/3.1.0
index 72664ab..03bbc7a 100644
--- a/winsup/cygwin/release/3.1.0
+++ b/winsup/cygwin/release/3.1.0
@@ -79,3 +79,6 @@ Bug Fixes
 - 64 bit only: Avoid collisions between memory maps created with shmat
   and Windows datastructures during fork.
   Addresses: https://cygwin.com/ml/cygwin/2019-08/msg00107.html
+
+- Make rmdir fail if its argument is a symlink.
+  Addresses: https://cygwin.com/ml/cygwin/2019-09/msg00221.html