XXX push upstream: no RLIMIT_AS on OpenBSD.

Index: compose/worker/asw-worker.c
--- compose/worker/asw-worker.c.orig
+++ compose/worker/asw-worker.c
@@ -37,6 +37,11 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
+/* no RLIMIT_AS on OpenBSD; RLIMIT_DATA is the closest match */
+#ifndef RLIMIT_AS
+#define RLIMIT_AS RLIMIT_DATA
+#endif
+
 #include "as-utils-private.h"
 #include "asc-globals.h"
 #include "asc-media.h"
