AC_PrecLand: add static create method

libraries/AC_PrecLand/AC_PrecLand.h

@@ -25,7 +25,6 @@ class AC_PrecLand
     friend class AC_PrecLand_SITL;
 
 public:
-
     // precision landing behaviours (held in PRECLAND_ENABLED parameter)
     enum PrecLandBehaviour {
         PRECLAND_BEHAVIOUR_DISABLED,
@@ -42,8 +41,15 @@ public:
         PRECLAND_TYPE_SITL,
     };
 
-    // constructor
-    AC_PrecLand(const AP_AHRS& ahrs, const AP_InertialNav& inav);
+    static AC_PrecLand create(const AP_AHRS& ahrs, const AP_InertialNav& inav) {
+        return AC_PrecLand{ahrs, inav};
+    }
+
+    constexpr AC_PrecLand(AC_PrecLand &&other) = default;
+
+    /* Do not allow copies */
+    AC_PrecLand(const AC_PrecLand &other) = delete;
+    AC_PrecLand &operator=(const AC_PrecLand&) = delete;
 
     // perform any required initialisation of landing controllers
     void init();
@@ -79,6 +85,8 @@ public:
     static const struct AP_Param::GroupInfo var_info[];
 
 private:
+    AC_PrecLand(const AP_AHRS& ahrs, const AP_InertialNav& inav);
+
     enum estimator_type_t {
         ESTIMATOR_TYPE_RAW_SENSOR = 0,
         ESTIMATOR_TYPE_KALMAN_FILTER = 1