AP_HAL_SITL: Use SITL, baro, INS and compass singletons

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

libraries/AP_HAL_SITL/SITL_State.cpp

@@ -73,10 +73,10 @@ void SITL_State::_sitl_setup(const char *home_str)
     fprintf(stdout, "Starting SITL input\n");
 
     // find the barometer object if it exists
-    _sitl = (SITL::SITL *)AP_Param::find_object("SIM_");
-    _barometer = (AP_Baro *)AP_Param::find_object("GND_");
-    _ins = (AP_InertialSensor *)AP_Param::find_object("INS_");
-    _compass = (Compass *)AP_Param::find_object("COMPASS_");
+    _sitl = AP::sitl();
+    _barometer = AP_Baro::get_instance();
+    _ins = AP_InertialSensor::get_instance();
+    _compass = Compass::get_singleton();
 #if AP_TERRAIN_AVAILABLE
     _terrain = reinterpret_cast<AP_Terrain *>(AP_Param::find_object("TERRAIN_"));
 #endif