ENH: Update ITK to include backported ExternalModule support

This will allow to build Slicer extensions based on custom ITK modules.

BRAINSTools:

$ git shortlog 26cb12b..c658c75 --no-merges
Hans J. Johnson (1):
BUG: Incorrect library specification

ITK:

$ git shortlog 087e938..0f346bf --no-merges
Bill Lorensen (1):
COMP: VTkGlue linker errors

Hans Johnson (2):
COMP: Need to propagate ITKGDCM
ENH: Missing ITK_OVERRIDE

Hyun Jae Kang (1):
BUG: Fix a compilation issue on ITK4 with FFTW and shared libraries

Lucas Gandel (1):
BUG: Fix external module BUILD_SHARED_LIBS status

Matthew McCormick (4):
ENH: Add ITKModuleExternal.cmake
ENH: Allow projects to build against an external module.
ENH: Add wrapping support for building modules externally.
BUG: Fix KWStyle test paths when building a module externally.

Zach Williamson (5):
ENH: Consolidate Library Dependencies
COMP: Add a missing link to Review module
COMP: Use correct linking macro in DCMTK
ENH: Use new linking system macros
PERF: Avoid searching private dependencies for include directories

git-svn-id: http://svn.slicer.org/Slicer4/trunk@24690 3bd1e089-480b-0410-8dfb-8563597acbee