Fix SF bug #1402308, segfault when using mmap(-1, ...)

This didn't crash on Linux, but valgrind complained.
I'm not sure if this test is valid on Windows.

Will backport.
diff --git a/Misc/ACKS b/Misc/ACKS
index 42fa409..ad77e03 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -529,6 +529,7 @@
 Neil Schemenauer
 David Scherer
 Gregor Schmid
+Ralf Schmitt
 Peter Schneider-Kamp
 Sam Schulenburg
 Stefan Schwarzer