sshd: allow UseBlocklist alias for UseBlacklist

blacklistd has been renamed to blocklistd upstream, and a future
import into FreeBSD will follow that change.  Support the new name
as an alias in config files.

Reviewed by:	bz, delphij
MFC after:	1 week
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D25865

crypto/openssh/servconf.c

@@ -660,6 +660,7 @@ static struct {
 	{ "rdomain", sRDomain, SSHCFG_ALL },
 	{ "casignaturealgorithms", sCASignatureAlgorithms, SSHCFG_ALL },
 	{ "useblacklist", sUseBlacklist, SSHCFG_GLOBAL },
+	{ "useblocklist", sUseBlacklist, SSHCFG_GLOBAL }, /* alias */
 	{ "noneenabled", sUnsupported, SSHCFG_ALL },
 	{ "hpndisabled", sDeprecated, SSHCFG_ALL },
 	{ "hpnbuffersize", sDeprecated, SSHCFG_ALL },

crypto/openssh/sshd_config.5

@@ -35,7 +35,7 @@
 .\"
 .\" $OpenBSD: sshd_config.5,v 1.282 2018/09/20 03:28:06 djm Exp $
 .\" $FreeBSD$
-.Dd $Mdocdate: September 20 2018 $
+.Dd $Mdocdate: July 28 2020 $
 .Dt SSHD_CONFIG 5
 .Os
 .Sh NAME
@@ -1602,6 +1602,11 @@ to the
 daemon.
 The default is
 .Cm no .
+For forward compatibility with an upcoming
+.Xr blacklistd
+rename, the
+.Cm UseBlocklist
+alias can be used instead.
 .It Cm UseDNS
 Specifies whether
 .Xr sshd 8