COMP: Update ITKv4 project

$ git shortlog 2379328..a8429da

Bradley Lowekamp (2):
      BUG: Fix uninitialized m_Spacing in SignedMaurerDistance
      BUG: Don't print null bias field

Ho Cheung (1):
      ENH: Improve mangling of itktiff library.

Matthew McCormick (4):
      COMP: Bump GCCXML version.
      Merge branch 'GccXML-4.8-release' into release
      ENH: Bump version to 4.4.2.
      BUG: Fix uninitialized variables in N4BiasFieldCorrectionImageFilter.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22468 3bd1e089-480b-0410-8dfb-8563597acbee