Fix VS2008 build issues with std::abs(__int64).
Fix VS2008 build issues with std::abs(__int64).

Since NUMFLUIDS is never going to be greater than MAXINT, we simply add
a static_cast<int> to avoid this build issue.

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