COMP: Use nullptr instead of 0 or NULL

The check converts the usage of null pointer constants (eg. NULL, 0) to
use the new C++11 nullptr keyword.

SRCDIR= #My local SRC
BLDDIR= #My local BLD

clang-tidy -p ${BLD}  $(find Modules/[A-J]*  -name "*.cxx" \|fgrep -v ThirdParty) -checks=-*,modernize-use-nullptr  -header-filter=.* -fix
clang-tidy -p ${BLD}  $(find Modules/[K-Z]*  -name "*.cxx" \|fgrep -v ThirdParty) -checks=-*,modernize-use-nullptr  -header-filter=.* -fix

Author: hjmjohnson

include/itkSingleImageCostFunction.hxx

@@ -30,9 +30,9 @@ template <class TImage>
 SingleImageCostFunction<TImage>
 ::SingleImageCostFunction()
 {
-  m_Image                 = 0;  // Provided by user
-  m_Interpolator          = 0;  // Configured in Initialize()
-  m_GradientImageFunction = 0;  // Configured in Initialize()
+  m_Image                 = nullptr;  // Provided by user
+  m_Interpolator          = nullptr;  // Configured in Initialize()
+  m_GradientImageFunction = nullptr;  // Configured in Initialize()
 }
 
 

include/itkSpeedFunctionToPathFilter.hxx

@@ -33,7 +33,7 @@ template <class TInputImage, class TOutputPath>
 SpeedFunctionToPathFilter<TInputImage,TOutputPath>
 ::SpeedFunctionToPathFilter()
 {
-  m_CurrentArrivalFunction = NULL;
+  m_CurrentArrivalFunction = nullptr;
 }