Pull up following revision(s) (requested by pavel in ticket #947):

	Makefile: revision 1.250
	usr.sbin/postinstall/postinstall: revision 1.51
	usr.sbin/postinstall/postinstall: revision 1.52
Return exit status 1 for failed chacks/fixes, 2 for errors. Suggested
by hubertf. Use exit status 3 for internal errors (misuse of internal
functions).
Add a check for obsolete sendmail in /etc/mailer.conf, installs a
fresh copy of the file if invoked as "fix". Not enabled by default.
Do not abort on exit code 1 from postinstall check, this is expected.
Reported, fix suggested and tested by David Holland.
(Why does "make build" invoke postinstall check on destdir is another
question, it does not seem to have much sense.)

Makefile

@@ -1,4 +1,4 @@
-#	$NetBSD: Makefile,v 1.246.2.2 2007/09/29 11:10:56 xtraeme Exp $
+#	$NetBSD: Makefile,v 1.246.2.3 2007/10/26 14:23:20 liamjfoy Exp $
 
 #
 # This is the top-level makefile for building NetBSD. For an outline of
@@ -158,7 +158,7 @@ _POSTINSTALL=	${.CURDIR}/usr.sbin/postinstall/postinstall
 
 postinstall-check: .PHONY
 	@echo "   === Post installation checks ==="
-	${HOST_SH} ${_POSTINSTALL} -s ${.CURDIR} -d ${DESTDIR}/ check
+	${HOST_SH} ${_POSTINSTALL} -s ${.CURDIR} -d ${DESTDIR}/ check; if [ $$? -gt 1 ]; then exit 1; fi
 	@echo "   ================================"
 
 postinstall-fix: .NOTMAIN .PHONY