STYLE: Prefer = default to explicitly trivial implementations

This check replaces default bodies of special member functions with
= default;. The explicitly defaulted function declarations enable more
opportunities in optimization, because the compiler might treat
explicitly defaulted functions as trivial.

Additionally, the C++11 use of = default more clearly expreses the
intent for the special member functions.

Modules/Filtering/FFT/include/itkComplexToComplex1DFFTImageFilter.h

@@ -92,7 +92,7 @@ class ITK_TEMPLATE_EXPORT ComplexToComplex1DFFTImageFilter : public ImageToImage
 
 protected:
   ComplexToComplex1DFFTImageFilter();
-  ~ComplexToComplex1DFFTImageFilter() override{};
+  ~ComplexToComplex1DFFTImageFilter() override = default;
 
   void
   PrintSelf(std::ostream & os, Indent indent) const override;

Modules/Filtering/FFT/include/itkForward1DFFTImageFilter.h

@@ -75,7 +75,7 @@ class ITK_TEMPLATE_EXPORT Forward1DFFTImageFilter : public ImageToImageFilter<TI
 
 protected:
   Forward1DFFTImageFilter();
-  ~Forward1DFFTImageFilter() override{};
+  ~Forward1DFFTImageFilter() override = default;
 
   void
   PrintSelf(std::ostream & os, Indent indent) const override;

Modules/Filtering/FFT/include/itkInverse1DFFTImageFilter.h

@@ -76,7 +76,7 @@ class ITK_TEMPLATE_EXPORT Inverse1DFFTImageFilter : public ImageToImageFilter<TI
 
 protected:
   Inverse1DFFTImageFilter();
-  ~Inverse1DFFTImageFilter() override{};
+  ~Inverse1DFFTImageFilter() override = default;
 
   void
   PrintSelf(std::ostream & os, Indent indent) const override;

Modules/Filtering/FFT/include/itkVnlInverse1DFFTImageFilter.h

@@ -59,8 +59,8 @@ class ITK_TEMPLATE_EXPORT VnlInverse1DFFTImageFilter : public Inverse1DFFTImageF
   void
   GenerateData() override;
 
-  VnlInverse1DFFTImageFilter() {}
-  ~VnlInverse1DFFTImageFilter() override{};
+  VnlInverse1DFFTImageFilter() = default;
+  ~VnlInverse1DFFTImageFilter() override = default;
 };
 
 } // end namespace itk