Fix sign function.
Fix sign function.

Thanks David Borland for the fix.

collects/VTK,cjh1/VTK,johnkit/vtk-dev,arnaudgelas/VTK,ashray/VTK-EVM,biddisco/VTK,jmerkow/VTK,SimVascular/VTK,sankhesh/VTK,arnaudgelas/VTK,mspark93/VTK,candy7393/VTK,sankhesh/VTK,gram526/VTK,mspark93/VTK,keithroe/vtkoptix,naucoin/VTKSlicerWidgets,hendradarwin/VTK,arnaudgelas/VTK,ashray/VTK-EVM,keithroe/vtkoptix,msmolens/VTK,demarle/VTK,demarle/VTK,jeffbaumes/jeffbaumes-vtk,biddisco/VTK,gram526/VTK,naucoin/VTKSlicerWidgets,naucoin/VTKSlicerWidgets,jmerkow/VTK,berendkleinhaneveld/VTK,naucoin/VTKSlicerWidgets,mspark93/VTK,collects/VTK,aashish24/VTK-old,sumedhasingla/VTK,johnkit/vtk-dev,daviddoria/PointGraphsPhase1,msmolens/VTK,spthaolt/VTK,berendkleinhaneveld/VTK,gram526/VTK,demarle/VTK,sankhesh/VTK,keithroe/vtkoptix,jeffbaumes/jeffbaumes-vtk,gram526/VTK,demarle/VTK,gram526/VTK,keithroe/vtkoptix,sankhesh/VTK,sumedhasingla/VTK,ashray/VTK-EVM,candy7393/VTK,demarle/VTK,berendkleinhaneveld/VTK,aashish24/VTK-old,johnkit/vtk-dev,SimVascular/VTK,berendkleinhaneveld/VTK,SimVascular/VTK,spthaolt/VTK,ashray/VTK-EVM,candy7393/VTK,berendkleinhaneveld/VTK,ashray/VTK-EVM,sankhesh/VTK,gram526/VTK,collects/VTK,aashish24/VTK-old,biddisco/VTK,naucoin/VTKSlicerWidgets,candy7393/VTK,msmolens/VTK,spthaolt/VTK,aashish24/VTK-old,keithroe/vtkoptix,hendradarwin/VTK,ashray/VTK-EVM,keithroe/vtkoptix,msmolens/VTK,biddisco/VTK,SimVascular/VTK,jmerkow/VTK,berendkleinhaneveld/VTK,daviddoria/PointGraphsPhase1,mspark93/VTK,arnaudgelas/VTK,jmerkow/VTK,hendradarwin/VTK,daviddoria/PointGraphsPhase1,SimVascular/VTK,SimVascular/VTK,daviddoria/PointGraphsPhase1,ashray/VTK-EVM,spthaolt/VTK,gram526/VTK,msmolens/VTK,sankhesh/VTK,sumedhasingla/VTK,sumedhasingla/VTK,candy7393/VTK,berendkleinhaneveld/VTK,cjh1/VTK,mspark93/VTK,hendradarwin/VTK,sumedhasingla/VTK,msmolens/VTK,spthaolt/VTK,demarle/VTK,cjh1/VTK,spthaolt/VTK,jeffbaumes/jeffbaumes-vtk,sumedhasingla/VTK,keithroe/vtkoptix,naucoin/VTKSlicerWidgets,hendradarwin/VTK,jeffbaumes/jeffbaumes-vtk,spthaolt/VTK,candy7393/VTK,hendradarwin/VTK,jeffbaumes/jeffbaumes-vtk,msmolens/VTK,mspark93/VTK,johnkit/vtk-dev,msmolens/VTK,biddisco/VTK,sumedhasingla/VTK,candy7393/VTK,daviddoria/PointGraphsPhase1,johnkit/vtk-dev,biddisco/VTK,johnkit/vtk-dev,collects/VTK,hendradarwin/VTK,keithroe/vtkoptix,cjh1/VTK,aashish24/VTK-old,arnaudgelas/VTK,demarle/VTK,biddisco/VTK,ashray/VTK-EVM,johnkit/vtk-dev,sumedhasingla/VTK,jmerkow/VTK,gram526/VTK,jmerkow/VTK,SimVascular/VTK,mspark93/VTK,mspark93/VTK,SimVascular/VTK,demarle/VTK,candy7393/VTK,daviddoria/PointGraphsPhase1,arnaudgelas/VTK,collects/VTK,jeffbaumes/jeffbaumes-vtk,cjh1/VTK,sankhesh/VTK,sankhesh/VTK,collects/VTK,aashish24/VTK-old,jmerkow/VTK,cjh1/VTK,jmerkow/VTK