Baro: fix example sketch

libraries/AP_Baro/examples/BARO_generic/BARO_generic.pde

@@ -34,6 +34,7 @@
 #include <AP_NavEKF.h>
 #include <AP_Scheduler.h>
 #include <AP_BattMonitor.h>
+#include <AP_RangeFinder.h>
 
 const AP_HAL::HAL& hal = AP_HAL_BOARD_DRIVER;