Initial len for the fmt=NULL case.

Patch from jjelen at redhat via bz#2687.  (OpenSSH never calls
setproctitle with a null format so len is always initialized).

openbsd-compat/setproctitle.c

@@ -125,7 +125,7 @@ setproctitle(const char *fmt, ...)
 #if SPT_TYPE != SPT_NONE
 	va_list ap;
 	char buf[1024], ptitle[1024];
-	size_t len;
+	size_t len = 0;
 	int r;
 	extern char *__progname;
 #if SPT_TYPE == SPT_PSTAT