Avoid access of uninitialized memory. This caused a bunch of crashes for me

while doing load testing of development branch where I'm working on some
performance improvements.


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@116978 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_iax2.c

@@ -6977,7 +6977,7 @@ static int socket_process(struct iax2_thread *thread)
 
 	/* allocate an iax_frame with 4096 bytes of data buffer */
 	fr = alloca(sizeof(*fr) + 4096);
-	fr->callno = 0;
+	memset(fr, 0, sizeof(*fr));
 	fr->afdatalen = 4096; /* From alloca() above */
 
 	/* Copy frequently used parameters to the stack */