Add RCS strings to kernel ipfilter files.

sys/netinet/ip_ftp_pxy.c

@@ -1,6 +1,8 @@
 /*
  * Simple FTP transparent proxy for in-kernel use.  For use with the NAT
  * code.
+ *
+ * $Id$
  */
 
 #define	isdigit(x)	((x) >= '0' && (x) <= '9')

sys/netinet/ipl.h

@@ -6,6 +6,7 @@
  * to the original author and the contributors.
  *
  * @(#)ipl.h	1.21 6/5/96
+ * $Id$
  */
 
 #ifndef	__IPL_H__

sys/netinet/mlf_ipl.c

@@ -4,6 +4,8 @@
  * Redistribution and use in source and binary forms are permitted
  * provided that this notice is preserved and due credit is given
  * to the original author and the contributors.
+ *
+ * $Id$
  */
 /*
  * 29/12/94 Added code from Marc Huber <huber@fzi.de> to allow it to allocate