Add some .Xrs to getloginclass(2).

MFC after:	1 month

lib/libc/sys/getloginclass.2

@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd March 6, 2011
+.Dd July 12, 2016
 .Dt GETLOGINCLASS 2
 .Os
 .Sh NAME
@@ -87,7 +87,10 @@ The caller tried to set the login class and was not the super-user.
 The size of the buffer is smaller than the result to be returned.
 .El
 .Sh SEE ALSO
-.Xr setusercontext 3
+.Xr ps 1 ,
+.Xr setusercontext 3 ,
+.Xr login.conf 5 ,
+.Xr rctl 8
 .Sh HISTORY
 The
 .Fn getloginclass