ftpd: add deprecation notice

Approved by:	gordon
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D26447

libexec/ftpd/ftpd.8

@@ -43,6 +43,16 @@
 .Op Fl T Ar maxtimeout
 .Op Fl t Ar timeout
 .Op Fl u Ar umask
+.Sh .Sh DEPRECATION NOTICE
+The
+.Fx
+base system
+.Nm
+is deprecated, and will be removed in
+.Fx 15.0.
+Users are advised to install the
+.Pa ftp/freebsd-ftpd
+port or package instead.
 .Sh DESCRIPTION
 The
 .Nm