Add John Regehr to Misc/ACKS for his help with finding integer overflows (issue #9530).
diff --git a/Misc/ACKS b/Misc/ACKS
index 3509126..6e38038 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -836,6 +836,7 @@
 Gareth Rees
 Steve Reeves
 Lennart Regebro
+John Regehr
 Federico Reghenzani
 Ofir Reichenberg
 Sean Reifschneider