Fix various compiler warnings:

* fix -Wunused-parameter
* fix -Wunused-function
* fix -Wunused-private-field
* fix -Wunused-variable
* fix -Winconsistent-missing-override

src/Mod/Measure/App/MeasureBase.h

@@ -67,7 +67,7 @@ public:
     virtual QString getResultString();
 
     virtual std::vector<std::string> getInputProps();
-    virtual App::Property* getResultProp() {return {};};
+    virtual App::Property* getResultProp() {return {};}
     virtual Base::Placement getPlacement();
 
     // Return the objects that are measured

src/Mod/Measure/App/MeasureLength.h

@@ -63,7 +63,7 @@ public:
     App::Property* getResultProp() override {return &this->Length;}
 
     // Return a placement for the viewprovider, just use the first element for now
-    Base::Placement getPlacement();
+    Base::Placement getPlacement() override;
 
     // Return the object we are measuring
     std::vector<App::DocumentObject*> getSubject() const override;