AP_Compass: allow override of COMPASS_AUTO_ROT

libraries/AP_Compass/AP_Compass.cpp

@@ -41,6 +41,10 @@ extern AP_HAL::HAL& hal;
  #define HAL_COMPASS_FILTER_DEFAULT 0 // turned off by default
 #endif
 
+#ifndef HAL_COMPASS_AUTO_ROT_DEFAULT
+#define HAL_COMPASS_AUTO_ROT_DEFAULT 2
+#endif
+
 const AP_Param::GroupInfo Compass::var_info[] = {
     // index 0 was used for the old orientation matrix
 
@@ -448,7 +452,7 @@ const AP_Param::GroupInfo Compass::var_info[] = {
     // @DisplayName: Automatically check orientation
     // @Description: When enabled this will automatically check the orientation of compasses on successful completion of compass calibration. If set to 2 then external compasses will have their orientation automatically corrected.
     // @Values: 0:Disabled,1:CheckOnly,2:CheckAndFix
-    AP_GROUPINFO("AUTO_ROT", 35, Compass, _rotate_auto, 2),
+    AP_GROUPINFO("AUTO_ROT", 35, Compass, _rotate_auto, HAL_COMPASS_AUTO_ROT_DEFAULT),
     
     AP_GROUPEND
 };