vtkWin32OpenGLRenderWindow: use size_t for integer storage of pointers
vtkWin32OpenGLRenderWindow: use size_t for integer storage of pointers

Also explicitly reinterpret_cast them.

Change-Id: I5ec4ae799e205e743c868cecffcf9ee400ded60f

sankhesh/VTK,candy7393/VTK,candy7393/VTK,candy7393/VTK,johnkit/vtk-dev,johnkit/vtk-dev,gram526/VTK,sumedhasingla/VTK,ashray/VTK-EVM,johnkit/vtk-dev,hendradarwin/VTK,msmolens/VTK,SimVascular/VTK,jmerkow/VTK,hendradarwin/VTK,candy7393/VTK,mspark93/VTK,sumedhasingla/VTK,ashray/VTK-EVM,SimVascular/VTK,hendradarwin/VTK,jmerkow/VTK,candy7393/VTK,keithroe/vtkoptix,keithroe/vtkoptix,gram526/VTK,jmerkow/VTK,jmerkow/VTK,gram526/VTK,keithroe/vtkoptix,msmolens/VTK,SimVascular/VTK,demarle/VTK,mspark93/VTK,demarle/VTK,johnkit/vtk-dev,sankhesh/VTK,gram526/VTK,hendradarwin/VTK,sankhesh/VTK,hendradarwin/VTK,keithroe/vtkoptix,msmolens/VTK,jmerkow/VTK,msmolens/VTK,sumedhasingla/VTK,ashray/VTK-EVM,msmolens/VTK,sumedhasingla/VTK,johnkit/vtk-dev,ashray/VTK-EVM,johnkit/vtk-dev,sankhesh/VTK,SimVascular/VTK,mspark93/VTK,sumedhasingla/VTK,msmolens/VTK,sankhesh/VTK,gram526/VTK,sumedhasingla/VTK,demarle/VTK,mspark93/VTK,mspark93/VTK,keithroe/vtkoptix,SimVascular/VTK,gram526/VTK,ashray/VTK-EVM,jmerkow/VTK,keithroe/vtkoptix,mspark93/VTK,jmerkow/VTK,keithroe/vtkoptix,candy7393/VTK,demarle/VTK,sankhesh/VTK,candy7393/VTK,msmolens/VTK,demarle/VTK,demarle/VTK,sumedhasingla/VTK,SimVascular/VTK,johnkit/vtk-dev,SimVascular/VTK,demarle/VTK,ashray/VTK-EVM,hendradarwin/VTK,gram526/VTK,ashray/VTK-EVM,mspark93/VTK,hendradarwin/VTK,SimVascular/VTK,sumedhasingla/VTK,ashray/VTK-EVM,demarle/VTK,sankhesh/VTK,gram526/VTK,keithroe/vtkoptix,mspark93/VTK,sankhesh/VTK,msmolens/VTK,jmerkow/VTK,candy7393/VTK