COMP: ImageRegistrationHistogramPlotter HistogramWriter visibility.

This fixes:

ImageRegistrationHistogramPlotter.cxx:171:7 warning: 'HistogramWriter'
declared with greater visibility than the type of its fild
'HistogramWriter::m_HistogramFileWriter'

Change-Id: I52936d5b35bfc2b30a2c7b21bb9b862406f3bba7
BUG: itkVTKTetrahedraMeshReader fails on a win64 build.

This patch fixed the windows 64 dashboard error:
http://open.cdash.org/testDetails.php?test=222975093&build=3131827 with the
following error msg:

"error during filter->Update(): itk::ExceptionObject (0000000000A2EF18)
Location: "unknown" File:
c:\dashboards\itk\modules\registration\fem\test\itkVTKTetrahedralMeshReader.hxx
Line: 282 Description: itk::ERROR: VTKTetrahedralMeshReader(0000000002B26FA0):
Error reading file:
C:/Dashboards/ITKVS10/ExternalData/Modules/Registration/FEM/test/Input/PBNRRMesh.vtk
numberOfCellPoints != 4 numberOfCellPoints= 4294967300.
VTKTetrahedralMeshReader can only read tetrahedra"

The variable type of numberOfCellPoints needs to be consistent.

Change-Id: I1705e94b8a8e76fe329b699e1fe25a282e48f5da
Merge topic 'HistogramWriter-visibility2'

2a3100c COMP: ImageRegistrationHistogramPlotter HistogramWriter visibility.
Merge topic 'BugFixForWinDashboardError'

10c5d80 BUG: itkVTKTetrahedraMeshReader fails on a win64 build.