csn1: Allow CHOICE elements to re-process the bits used for the choice

This is a port of wireshark.git commit
2f024256bf337400ef3a82fa75e6d48d5707e059.

From 78516187d821b8d19d16987b1d6bc855ee7cbe10 Mon Sep 17 00:00:00 2001
From: Sylvain Munaut <tnt@246tNt.com>
Date: Sat, 4 Feb 2012 10:00:22 +0100
Subject: [PATCH 4/6] packet-csn1: Allow CHOICE elements to re-process the bits used for the choice

We may want to display more detail, or the sub-element should be
displayed with its headers or whatever ...

Change-Id: I3a5a95d5f918b8f17a2400a6d0c4d855ecacea7e
diff --git a/src/csn1.h b/src/csn1.h
index 39e6625..e927076 100644
--- a/src/csn1.h
+++ b/src/csn1.h
@@ -212,6 +212,7 @@
 {
   guint8     bits;
   guint8     value;
+  gboolean   keep_bits;
   CSN_DESCR descr;
 } CSN_ChoiceElement_t;