mail/qmail-rblchk: fix build on FreeBSD 15

- set LICENSE
 - include errno.h to get errno, instead of declaring it as an extern
   variable.

mail/qmail-rblchk/Makefile

@@ -1,6 +1,6 @@
 PORTNAME=	qmail-rblchk
 PORTVERSION=	2.4.1
-PORTREVISION=	2
+PORTREVISION=	3
 CATEGORIES=	mail
 MASTER_SITES=	http://www.morettoni.net/qmail/ \
 		LOCAL/ehaupt
@@ -9,6 +9,9 @@ MAINTAINER=	ports@FreeBSD.org
 COMMENT=	Qmail RBL filter
 WWW=		http://www.morettoni.net/qmail-rblchk.en.html
 
+# so says qmail-rblchk.c
+LICENSE=	BSD2CLAUSE
+
 USES=		groff qmail:run
 
 ALL_TARGET=	default

mail/qmail-rblchk/files/patch-error.h

@@ -0,0 +1,11 @@
+--- error.h.orig	2024-09-25 10:49:27 UTC
++++ error.h
+@@ -1,7 +1,7 @@
+ #ifndef ERROR_H
+ #define ERROR_H
+ 
+-extern int errno;
++#include <errno.h>
+ 
+ extern int error_intr;
+ extern int error_nomem;