#678250: Make mmap flush a noop on ACCESS_READ and ACCESS_COPY.

Patch by Sébastien Sablé.  This solves a test_mmap failure on AIX.
diff --git a/Misc/NEWS b/Misc/NEWS
index 1889478..15c0bb3 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -87,6 +87,8 @@
 Extensions
 ----------
 
+- Issue #678250: Make mmap flush a noop on ACCESS_READ and ACCESS_COPY.
+
 - Issue #9054: Fix a crash occurring when using the pyexpat module
   with expat version 2.0.1.