AP_Landing: Add a servo override interface and PID logging interface

libraries/AP_Landing/AP_Landing.cpp

@@ -288,6 +288,29 @@ bool AP_Landing::is_expecting_impact(void) const
     }
 }
 
+// returns true when the landing library has overriden any servos
+bool AP_Landing::override_servos(void) {
+    if (!flags.in_progress) {
+        return false;
+    }
+
+    switch (type) {
+    case TYPE_STANDARD_GLIDE_SLOPE:
+    default:
+        return false;
+    }
+}
+
+// returns a PID_Info object if there is one available for the selected landing
+// type, otherwise returns a nullptr, indicating no data to be logged/sent
+const DataFlash_Class::PID_Info* AP_Landing::get_pid_info(void) const
+{
+    switch (type) {
+    case TYPE_STANDARD_GLIDE_SLOPE:
+    default:
+        return nullptr;
+    }
+}
 
 /*
   a special glide slope calculation for the landing approach

libraries/AP_Landing/AP_Landing.h

@@ -74,6 +74,7 @@ public:
             const float height, const float sink_rate, const float wp_proportion, const uint32_t last_flying_ms, const bool is_armed, const bool is_flying, const bool rangefinder_state_in_range);
     void adjust_landing_slope_for_rangefinder_bump(AP_Vehicle::FixedWing::Rangefinder_State &rangefinder_state, Location &prev_WP_loc, Location &next_WP_loc, const Location &current_loc, const float wp_distance, int32_t &target_altitude_offset_cm);
     void setup_landing_glide_slope(const Location &prev_WP_loc, const Location &next_WP_loc, const Location &current_loc, int32_t &target_altitude_offset_cm);
+    bool override_servos(void);
     void check_if_need_to_abort(const AP_Vehicle::FixedWing::Rangefinder_State &rangefinder_state);
     bool request_go_around(void);
     bool is_flaring(void) const;
@@ -104,6 +105,7 @@ public:
     void set_initial_slope(void) { initial_slope = slope; }
     bool is_expecting_impact(void) const;
     void log(void) const;
+    const DataFlash_Class::PID_Info * get_pid_info(void) const;
 
     // landing altitude offset (meters)
     float alt_offset;