AP_Compass: added set_offsets() interface

this will be used by Replay to prevent the need for saving parameters

libraries/AP_Compass/Compass.cpp

@@ -289,6 +289,15 @@ Compass::init()
     return true;
 }
 
+void
+Compass::set_offsets(uint8_t i, const Vector3f &offsets)
+{
+    // sanity check compass instance provided
+    if (i < COMPASS_MAX_INSTANCES) {
+        _offset[i].set(offsets);
+    }
+}
+
 void
 Compass::set_and_save_offsets(uint8_t i, const Vector3f &offsets)
 {

libraries/AP_Compass/Compass.h

@@ -87,6 +87,13 @@ public:
     ///
     float calculate_heading(const Matrix3f &dcm_matrix) const;
 
+    /// Sets offset x/y/z values.
+    ///
+    /// @param  i                   compass instance
+    /// @param  offsets             Offsets to the raw mag_ values.
+    ///
+    void set_offsets(uint8_t i, const Vector3f &offsets);
+
     /// Sets and saves the compass offset x/y/z values.
     ///
     /// @param  i                   compass instance