AP_HAL_AVR: main calls system_initialized

libraries/AP_HAL_AVR/AP_HAL_AVR_Main.h

@@ -7,6 +7,7 @@
     int main (void) {\
 	hal.init(0, NULL);			\
         setup();\
+        hal.scheduler->system_initialized(); \
         for(;;) loop();\
         return 0;\
     }\