Fix MTime bug in vtkTextMapper.
Fix MTime bug in vtkTextMapper.

See http://www.vtk.org/Bug/view.php?id=15303. Thanks to
Luc Habert for the report and patch.

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