COMP: Replace ITK_TEMPLATE_TXX with ITK_MANUAL_INSTANTIATION

Addresses:

  ITK/Modules/Core/Common/include/itkMacro.h:500:27: error: token ""error
  ITK_TEMPLATE_TXX is no longer a supported identifier, you should replace
  with ITK_MANUAL_INSTANTIATION as a replacement"" is not valid in
  preprocessor expressions

Author: thewtex

include/itkPhysicalCentralDifferenceImageFunction.h

@@ -147,7 +147,7 @@ class ITK_EXPORT PhysicalCentralDifferenceImageFunction :
 
 } // end namespace itk
 
-#if ITK_TEMPLATE_TXX
+#ifndef ITK_MANUAL_INSTANTIATION
 # include "itkPhysicalCentralDifferenceImageFunction.hxx"
 #endif