Issue 12404: Remove C89 incompatible code from mmap module.

Patch by Akira Kitada.
diff --git a/Misc/NEWS b/Misc/NEWS
index 60405dd..9dfd0ac 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -25,6 +25,9 @@
 Library
 -------
 
+- Issue #12404: Remove C89 incompatible code from mmap module. Patch by Akira
+  Kitada.
+
 - Issue #12383: Fix subprocess module with env={}: don't copy the environment
   variables, start with an empty environment.