moved io and signal and IAR-GCC checks from driver files into contiki include file

platform/sky/dev/button-sensor.c

@@ -30,16 +30,11 @@
  *
  * @(#)$Id: button-sensor.c,v 1.4 2010/01/14 20:01:19 nifi Exp $
  */
+#include "contiki.h"
 #include "lib/sensors.h"
 #include "dev/hwconf.h"
 #include "dev/button-sensor.h"
 
-#ifdef __IAR_SYSTEMS_ICC__
-#include <msp430.h>
-#else
-#include <signal.h>
-#endif
-
 const struct sensors_sensor button_sensor;
 
 static struct timer debouncetimer;