COMP: Remove deprecated 'register' keyword

See discussion form June 28, 2013
http://public.kitware.com/pipermail/cmake-developers/2013-June/007602.html

Modules/Core/Common/include/itkNeighborhoodIterator.hxx:102:3: warning:
'register' storage class specifier is deprecated [-Wdeprecated-register]

Change-Id: Ifc70628ac1b663c1bb8fea0577bd609121761a2d
Merge topic 'RemoveRegisterKeyword'

8703432e COMP: Remove deprecated 'register' keyword