ZyklonB, kike: Use pledge(2) in OpenBSD

degesch has something like "stdio wpath cpath inet tty proc exec"
but given that it's user-extensible and very annoying for users to
have it crash, I'm leaving it unrestricted for now.

zyklonb.c

@@ -2023,6 +2023,12 @@ main (int argc, char *argv[])
 	ctx.signal_event.user_data = &ctx;
 	poller_fd_set (&ctx.signal_event, POLLIN);
 
+#if OpenBSD >= 201605
+	// cpath is for creating the plugin home directory
+	if (pledge ("stdio rpath cpath inet proc exec", NULL))
+		exit_fatal ("%s: %s", "pledge", strerror (errno));
+#endif
+
 	plugin_load_all_from_config (&ctx);
 	if (!parse_config (&ctx, &e)
 	 || !irc_connect (&ctx, &e))