Filter: add override keyword

libraries/Filter/AverageFilter.h

@@ -33,7 +33,7 @@ public:
     };
 
     // apply - Add a new raw value to the filter, retrieve the filtered result
-    virtual T        apply(T sample);
+    virtual T        apply(T sample) override;
 
     // reset - clear the filter
     virtual void        reset();

libraries/Filter/DerivativeFilter.h

@@ -39,7 +39,7 @@ public:
     float slope(void);
 
     // reset - clear the filter
-    virtual void        reset();
+    virtual void        reset() override;
 
 private:
     bool            _new_data;

libraries/Filter/FilterWithBuffer.h

@@ -31,10 +31,10 @@ public:
     FilterWithBuffer();
 
     // apply - Add a new raw value to the filter, retrieve the filtered result
-    virtual T apply(T sample);
+    virtual T apply(T sample) override;
 
     // reset - clear the filter
-    virtual void reset();
+    virtual void reset() override;
 
     // get filter size
     uint8_t get_filter_size() const {

libraries/Filter/ModeFilter.h

@@ -30,7 +30,7 @@ public:
     ModeFilter(uint8_t return_element);
 
     // apply - Add a new raw value to the filter, retrieve the filtered result
-    virtual T        apply(T sample);
+    virtual T        apply(T sample) override;
 
     // get - get latest filtered value from filter (equal to the value returned by latest call to apply method)
     virtual T        get() const {