Preserve PKT_ALLOC flag inside PACKET_RECYCLE().

The PKT_ALLOC flag was being cleared by PACKET_RECYCLE(), which could
then result in a packet being pushed back to the Packet ring buffer
incorrectly.

src/decode.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2007-2012 Open Information Security Foundation
+/* Copyright (C) 2007-2013 Open Information Security Foundation
  *
  * You can copy, redistribute or modify this Program under the terms of
  * the GNU General Public License version 2 as published by the Free
@@ -639,7 +639,7 @@ typedef struct DecodeThreadVars_
         (p)->dp = 0;                            \
         (p)->proto = 0;                         \
         (p)->recursion_level = 0;               \
-        (p)->flags = 0;                         \
+        (p)->flags = (p)->flags & PKT_ALLOC;    \
         (p)->flowflags = 0;                     \
         (p)->pkt_src = 0;                       \
         FlowDeReference(&((p)->flow));          \