warnign fixe for stat_display

src/include/lwip/opt.h

@@ -417,6 +417,7 @@ a lot of data that needs to be copied, this should be set high. */
 #define PBUF_STATS	0
 #define SYS_STATS	0
 #define RAW_STATS	0
+#define LWIP_STATS_DISPLAY	0
 
 #endif /* LWIP_STATS */
 

src/include/lwip/stats.h

@@ -147,6 +147,8 @@ void stats_init(void);
 /* Display of statistics */
 #if LWIP_STATS_DISPLAY
 void stats_display(void);
+#else
+#define stats_display()
 #endif
 
 #endif /* __LWIP_STATS_H__ */