disallow infinite call chains of exit_cleanup

(this happened when the pipe to rsync got broken, because rsync would
then try to write to stderr, find out it didn't work, and call exit_cleanup,
which would then try it all over again... oops.

net/rsync/patches/patch-cleanup_c

@@ -0,0 +1,16 @@
+$OpenBSD: patch-cleanup_c,v 1.1 2002/12/14 18:06:58 espie Exp $
+--- cleanup.c.orig	Sat Dec 14 18:55:23 2002
++++ cleanup.c	Sat Dec 14 18:55:55 2002
+@@ -43,6 +43,12 @@ void _exit_cleanup(int code, const char 
+ 	int ocode = code;
+ 	extern int keep_partial;
+ 	extern int log_got_error;
++	static int in_cleanup = 0;
++
++	/* forbid recursive calls */
++	if (in_cleanup)
++		return;
++	in_cleanup = 1;
+ 
+ 	signal(SIGUSR1, SIG_IGN);
+ 	signal(SIGUSR2, SIG_IGN);