Add dot ('.') in usernames too for consistency with adduser/useradd.

Noted by Brian Poole

src/etc/security

@@ -1,6 +1,6 @@
 #!/bin/sh -
 #
-#	$OpenBSD: security,v 1.57 2003/06/12 19:11:57 millert Exp $
+#	$OpenBSD: security,v 1.58 2003/06/13 15:55:57 millert Exp $
 #	from: @(#)security	8.1 (Berkeley) 6/9/93
 #
 
@@ -31,7 +31,7 @@ awk -F: '{
 		next;
 	if ($1 == "")
 		printf("Line %d has an empty login field:\n%s\n", NR, $0);
-	else if ($1 !~ /^[A-Za-z0-9_][A-Za-z0-9_-]*\$?$/)
+	else if ($1 !~ /^[A-Za-z0-9_][A-Za-z0-9_-\.]*\$?$/)
 		printf("Login %s has non-alphanumeric characters.\n", $1);
 	if (length($1) > 31)
 		printf("Login %s has more than 31 characters.\n", $1);