AP_Common: added HomeState enum from copter

libraries/AP_Common/AP_Common.h

@@ -116,6 +116,15 @@ struct PACKED Location {
     int32_t lng;                                        ///< param 4 - Longitude * 10**7
 };
 
+/*
+  home states. Used to record if user has overridden home position.
+*/
+enum HomeState {
+    HOME_UNSET,                 // home is unset, no GPS positions yet received
+    HOME_SET_NOT_LOCKED,        // home is set to EKF origin or armed location (can be moved)
+    HOME_SET_AND_LOCKED         // home has been set by user, cannot be moved except by user initiated do-set-home command
+};
+
 //@}
 
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