ENH: ITKv5 override consistency

Provide remove virtual and override

Use clang-tidy to add ITK_OVERRIDE, and to remove
redundant virtual on functions.

cd ../ITK;
clang-tidy -p ITK-clangtidy $find Modules/[A-J]*  -name *.cxx |fgrep -v ThirdParty) -checks=-*,modernize-use-override  -header-filter=.* -fix
clang-tidy -p ITK-clangtidy $(find Modules/[K-Z]*  -name *.cxx |fgrep -v ThirdParty) -checks=-*,modernize-use-override  -header-filter=.* -fix

https://stackoverflow.com/questions/39932391/virtual-override-or-both-c

When you override a function you don't technically need to write either virtual
or override.

The original base class declaration needs the keyword virtual to mark it as virtual.

In the derived class the function is virtual by way of having the ¹same type as
the base class function.

However, an override can help avoid bugs by producing a compilation error when
the intended override isn't technically an override. E.g. that the function
type isn't exactly like the base class function. Or that a maintenance of the
base class changes that function's type, e.g. adding a defaulted argument.

In the same way, a virtual keyword in the derived class can make such a bug
more subtle, by ensuring that the function is still is virtual in further
derived classes.

So the general advice is,

virtual for the base class function declaration.
This is technically necessary.

Use override (only) for a derived class' override.
This helps with maintenance.

include/itkAdditiveGaussianNoiseMeshFilter.h

@@ -79,7 +79,7 @@ public MeshToMeshFilter< TInput, TOutput >
 protected:
 
   AdditiveGaussianNoiseMeshFilter();
-  ~AdditiveGaussianNoiseMeshFilter() override{}
+  ~AdditiveGaussianNoiseMeshFilter() ITK_OVERRIDE{}
 
   void PrintSelf(std::ostream & os, Indent indent) const ITK_OVERRIDE;
 

include/itkAdditiveGaussianNoiseQuadEdgeMeshFilter.h

@@ -72,7 +72,7 @@ class AdditiveGaussianNoiseQuadEdgeMeshFilter:
 protected:
 
   AdditiveGaussianNoiseQuadEdgeMeshFilter();
-  ~AdditiveGaussianNoiseQuadEdgeMeshFilter() override{}
+  ~AdditiveGaussianNoiseQuadEdgeMeshFilter() ITK_OVERRIDE{}
 
   void PrintSelf(std::ostream & os, Indent indent) const ITK_OVERRIDE;