get things building with glibc-2.8

http://bugs.gentoo.org/248100

--- include/common.h
+++ include/common.h
@@ -23,6 +23,7 @@
 #ifndef __COMMON_H
 #define __COMMON_H
 
+#include <limits.h>
 #include <netinet/in.h>
 #include <time.h>
 #include "queue.h"