audit: use define's for audit version

Give names to the audit versions. Just something for a userspace
programmer to know what the version provides.

Signed-off-by: Eric Paris <[e-mail]>

include/uapi/linux/audit.h

···
 #define AUDIT_STATUS_RATE_LIMIT		0x0008
 #define AUDIT_STATUS_BACKLOG_LIMIT	0x0010
 #define AUDIT_STATUS_BACKLOG_WAIT_TIME	0x0020
+
+#define AUDIT_VERSION_BACKLOG_LIMIT	1
+#define AUDIT_VERSION_BACKLOG_WAIT_TIME	2
+#define AUDIT_VERSION_LATEST AUDIT_VERSION_BACKLOG_WAIT_TIME
+
 				/* Failure-to-log actions */
 #define AUDIT_FAIL_SILENT	0
 #define AUDIT_FAIL_PRINTK	1

kernel/audit.c

···
 		s.backlog_limit		= audit_backlog_limit;
 		s.lost			= atomic_read(&audit_lost);
 		s.backlog		= skb_queue_len(&audit_skb_queue);
-		s.version		= 2;
+		s.version		= AUDIT_VERSION_LATEST;
 		s.backlog_wait_time	= audit_backlog_wait_time;
 		audit_send_reply(NETLINK_CB(skb).portid, seq, AUDIT_GET, 0, 0,
 				 &s, sizeof(s));