Cygwin: improve release text for FILE issue

Add a note in terms of 3.4.0 compatibility.

Suggested-by: Markus Mützel <markus.muetzel@gmx.de>
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/release/3.4.1

@@ -6,5 +6,7 @@ Bug Fixes
   Addresses: https://cygwin.com/pipermail/cygwin/2022-December/252619.html
 
 - Fix a backward incompatibility problem in the definition of the
-  base type of the stdio type FILE.
+  base type of the stdio type FILE.  This requires that C++ binaries
+  compiled under Cygwin 3.4.0 having a public facing interface using
+  FILE need to be recompiled.
   Addresses: https://savannah.gnu.org/bugs/index.php?63480