Fix bug in marshal where bad data would cause a segfault due to
lack of an infinite recursion check.

Contributed by Damien Miller at Google.
diff --git a/Misc/ACKS b/Misc/ACKS
index b47ec6e..b0a0372 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -429,6 +429,7 @@
 Greg McFarlane
 Michael McLay
 Gordon McMillan
+Damien Miller
 Jay T. Miller
 Chris McDonough
 Andrew McNamara