COMP: Fix unused-local-typedefs warnings

From: Jean-Christophe Fillion-Robin <jchris.fillionr@kitware.com>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23138 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: Fix visibility warning in DiffusionTensor3DRead

Remove warning: ‘itk::DiffusionTensor3DRead<float>’ declared with greater
visibility than the type of its field ‘itk::DiffusionTensor3DRead<float>::m_Reader’

Due to the fact that itkDiffusionTensor3DRead was declaring a private
variable of type itkImageFileReader<DiffusionImageType>::Pointer and that
this class was declared with ITK_ABI_EXPORT, we had to add ITK_ABI_EXPORT
to the declaration of itkDiffusionTensor3DRead to remove the previously
described warning when ResampleDTIVolume was compiled (shared object).

From: Francois Budin <fbudin@unc.edu>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23139 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: Fix "unused-local"typedefs" warning and update ITKv4

Commit r23121 removed the addition of "-Wno-unused-local-typedefs",
this commit is an attempt to clean most of the warnings. It also
updates the ITKv4 external project so that it checks out the Slicer ITK
fork including the ITK patch currently in review. See [1], [2]

$ git shortlog 01661ccf99..184b1257ad
Jean-Christophe Fillion-Robin (3):
      COMP: Properly fix unused-local-typedefs warning using unused attribute.
      COMP: Fix "unused-local-typedefs" warnings
      COMP: Backport double conversion fix for "unused-local-typedefs" warning

[1] http://review.source.kitware.com/#/c/15379/
[2] http://review.source.kitware.com/#/c/15380/

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23140 3bd1e089-480b-0410-8dfb-8563597acbee