Note that CDRs are immutable once a bridge is torn down

CDRs cannot be modified after a bridge is torn down, (e.g. after
Dial() returns) even though the CDR() function may be called. Since
modifying the CDR code to change this behavior could very easily
break all kinds of things, this patch just documents this limitation.

(closes issues ASTERISK-16923)
Review: https://reviewboard.asterisk.org/r/1720/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@354749 65c4cc65-6c06-0410-ace0-fbb531ad65f3

funcs/func_cdr.c

@@ -140,7 +140,9 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 			with this function, and this variable will be stored on the cdr.</para>
 			<note><para>For setting CDR values, the <literal>l</literal> flag does not apply to
 			setting the <literal>accountcode</literal>, <literal>userfield</literal>, or
-			<literal>amaflags</literal>.</para></note>
+			<literal>amaflags</literal>.</para><para>CDRs can only be modified before the bridge
+			between two channels is torn down. For example, CDRs may not be modified after the
+			<literal>Dial</literal> application has returned.</para></note>
 			<para>Raw values for <literal>disposition</literal>:</para>
 			<enumlist>
 				<enum name="0">