ENH: Update ITKv4 version to current release branch (7c3a15e-2014-09-03)

$ git shortlog 372991d..7c3a15ebc --no-merges
Bradley Lowekamp (2):
      BUG: Use METER of sCAL scale unit
      BUG: Use PNG_SCALE_METER for PNG sCAL unit

Christopher Mullins (1):
      COMP: Allows latex to compile for ITKSoftwareGuide

KWSys Robot (2):
      KWSys 2014-07-18 (65b36ede)
      KWSys 2014-08-04 (e787837a)

Matthew McCormick (9):
      BUG: Fix alpha assignment for RGBA TIFF.
      BUG: Improve thread-safety and performance of PCAShapeSignedDistanceFunction.
      DOC: itk::statistics -> itk::Statistics.
      DOC: Remove duplicate text in LaplacianRecursiveGaussian example.
      DOC: Fix Software Guide page overruns in IterativeClosestPoint{1,2}.cxx.
      BUG: TransformFileReader does not clear its TransformList.
      BUG: Prevent dangling pointer in HDF5TransformIO.
      COMP: Fix missing prefix in ITKv3ImageRegistration20Test.
      BUG: Do not return SmartPointers in TimeVaryingVelocityFieldTransform

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23664 3bd1e089-480b-0410-8dfb-8563597acbee