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 <eparis@redhat.com>
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index 14afb0d..3e1fbe9 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -320,6 +320,11 @@
 #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