CPUInfo: fixed build

Tools/CPUInfo/CPUInfo.pde

@@ -30,6 +30,7 @@
 #include <AP_Airspeed.h>
 #include <AP_Vehicle.h>
 #include <AP_Mission.h>
+#include <AP_Terrain.h>
 #include <AP_ADC_AnalogSource.h>
 
 const AP_HAL::HAL& hal = AP_HAL_BOARD_DRIVER;