Update introductory comment for audit pipes.

MFC after:	2 months
Sponsored by:	Apple, Inc.

sys/security/audit/audit_pipe.c

@@ -57,10 +57,10 @@ __FBSDID("$FreeBSD$");
 
 /*
  * Implementation of a clonable special device providing a live stream of BSM
- * audit data.  This is a "tee" of the data going to the file.  It provides
- * unreliable but timely access to audit events.  Consumers of this interface
- * should be very careful to avoid introducing event cycles.  Consumers may
- * express interest via a set of preselection ioctls.
+ * audit data.  Consumers receive a "tee" of the system audit trail by
+ * default, but may also define alternative event selections using ioctls.
+ * This interface provides unreliable but timely access to audit events.
+ * Consumers should be very careful to avoid introducing event cycles.
  */
 
 /*