Remove use of KWSys cstddef compatiblilty header
Remove use of KWSys cstddef compatiblilty header

In the only source where we include it we already have <stddef.h>
anyway.  Just drop the extra inclusion.

SimVascular/VTK,sankhesh/VTK,keithroe/vtkoptix,keithroe/vtkoptix,mspark93/VTK,sumedhasingla/VTK,keithroe/vtkoptix,SimVascular/VTK,SimVascular/VTK,sankhesh/VTK,sumedhasingla/VTK,sumedhasingla/VTK,sankhesh/VTK,gram526/VTK,gram526/VTK,keithroe/vtkoptix,sumedhasingla/VTK,gram526/VTK,mspark93/VTK,gram526/VTK,mspark93/VTK,sankhesh/VTK,keithroe/vtkoptix,gram526/VTK,mspark93/VTK,SimVascular/VTK,gram526/VTK,mspark93/VTK,keithroe/vtkoptix,sankhesh/VTK,SimVascular/VTK,keithroe/vtkoptix,sumedhasingla/VTK,sumedhasingla/VTK,keithroe/vtkoptix,gram526/VTK,SimVascular/VTK,sumedhasingla/VTK,mspark93/VTK,SimVascular/VTK,gram526/VTK,sankhesh/VTK,mspark93/VTK,sankhesh/VTK,mspark93/VTK,sankhesh/VTK,SimVascular/VTK,sumedhasingla/VTK