Fixed build errors.

Tested on hello-world example.

Author: PIlin

platform/arduino/contiki-conf.h

@@ -194,9 +194,5 @@ typedef unsigned short clock_time_t;
 typedef unsigned short uip_stats_t;
 typedef unsigned long off_t;
 
-void clock_delay(unsigned int us2);
-void clock_wait(int ms10);
-void clock_set_seconds(unsigned long s);
-unsigned long clock_seconds(void);
 
 #endif /* __CONTIKI_CONF_H__ */