Document callout_pending() macro.

MFC after:	1 week

share/man/man9/timeout.9

@@ -36,7 +36,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd September 10, 1996
+.Dd December 29, 2004
 .Dt TIMEOUT 9
 .Os
 .Sh NAME
@@ -73,6 +73,7 @@ struct callout_handle handle = CALLOUT_HANDLE_INITIALIZER(&handle)
 .Fn callout_drain "struct callout *c"
 .Ft void
 .Fn callout_reset "struct callout *c" "int ticks" "timeout_t *func" "void *arg"
+.Fn callout_pending "struct callout *c"
 .Sh DESCRIPTION
 The function
 .Fn timeout
@@ -218,6 +219,10 @@ first calls
 to disestablish the callout, and then establishes a new callout in the
 same manner as
 .Fn timeout .
+.Pp
+The macro
+.Fn callout_pending
+can be used to check whether callout is pending.
 .Sh RETURN VALUES
 The
 .Fn timeout