Enable PAM option by default on OS X as sudo does not work without it otherwise.

Reported by @kusalananda on twitter, confirmed by comparing the output of sudo
-V as root between Apple bundled version & pkgsrc version.
It's not possible to use sudo from a unprivileged build as sudo expects to be
setuid to root so mark it as NOT_FOR_UNPRIVILEGED.

Reviewed by wiz@

security/sudo/Makefile

@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.145 2015/02/11 09:11:59 spz Exp $
+# $NetBSD: Makefile,v 1.146 2015/07/11 15:12:27 sevan Exp $
 #
 
 DISTNAME=		sudo-1.7.10p9
@@ -51,6 +51,7 @@ SPECIAL_PERMS+=		bin/sudo ${SETUID_ROOT_PERMS}
 SPECIAL_PERMS+=		bin/sudoreplay ${REAL_ROOT_USER} ${REAL_ROOT_GROUP} 511
 
 INSTALLATION_DIRS+=	${DOCDIR} ${EGDIR}
+NOT_FOR_UNPRIVILEGED=	yes
 
 post-install:
 	${INSTALL_DATA} ${WRKSRC}/UPGRADE ${DESTDIR}${PREFIX}/${DOCDIR}

security/sudo/options.mk

@@ -1,4 +1,4 @@
-# $NetBSD: options.mk,v 1.17 2009/02/14 19:30:33 tonnerre Exp $
+# $NetBSD: options.mk,v 1.18 2015/07/11 15:12:27 sevan Exp $
 #
 
 PKG_OPTIONS_VAR=	PKG_OPTIONS.sudo
@@ -10,6 +10,10 @@ PKG_OPTIONS_GROUP.auth=	kerberos pam skey
 PKG_SUGGESTED_OPTIONS=	skey
 .endif
 
+.if ${OPSYS} == "Darwin"
+PKG_SUGGESTED_OPTIONS=	pam
+.endif
+
 .include "../../mk/bsd.options.mk"
 
 .if !empty(PKG_OPTIONS:Mpam)