Switch to 'file' backend for aliases table for default configuration.

Ok gilles@ jung@ millert@

src/etc/mail/smtpd.conf

@@ -1,4 +1,4 @@
-#	$OpenBSD: smtpd.conf,v 1.7 2014/03/12 18:21:34 tedu Exp $
+#	$OpenBSD: smtpd.conf,v 1.8 2015/12/21 16:25:44 sunil Exp $
 
 # This is the smtpd server system-wide configuration file.
 # See smtpd.conf(5) for more information.
@@ -7,7 +7,7 @@
 #
 listen on lo0
 
-table aliases db:/etc/mail/aliases.db
+table aliases file:/etc/mail/aliases
 
 # Uncomment the following to accept external mail for domain "example.org"
 #