Removed unused 'hex_digits' constant
Removed unused 'hex_digits' constant

Found by clang's new -Wunused-const-variable

Change-Id: I426b9fb0588e6a425815b6875edfa3eb367c43cd

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