Missing include, breaks with ports-gcc

Index: src/script/script.h
--- src/script/script.h.orig
+++ src/script/script.h
@@ -26,6 +26,7 @@
 
 #include "CBot/CBot.h"
 
+#include <limits>
 #include <memory>
 #include <string>
 #include <boost/optional.hpp>
