[newlib-cygwin] Document the last bug fix

[Ken Brown]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=6061f9c76f242f851e1d5119e1cbdef683dd0aa4

commit 6061f9c76f242f851e1d5119e1cbdef683dd0aa4
Author: Ken Brown <kbrown@cornell.edu>
Date:   Fri Sep 27 13:36:45 2019 -0400

    Document the last bug fix

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 03bbc7a..7f88c53 100644
--- a/winsup/cygwin/release/3.1.0
+++ b/winsup/cygwin/release/3.1.0
@@ -82,3 +82,6 @@ Bug Fixes
 
 - Make rmdir fail if its argument is a symlink.
   Addresses: https://cygwin.com/ml/cygwin/2019-09/msg00221.html
+
+- Fix an assertion failure on an invalid path.
+  Addresses: https://cygwin.com/ml/cygwin/2019-09/msg00228.html