Update ITK superbuild version to 4.8 release
Update ITK superbuild version to 4.8 release

Change-Id: I74e731b70f4e3dba9b31a1196e4fad7cec5c527b

blowekamp/SimpleITK,blowekamp/SimpleITK,richardbeare/SimpleITK,richardbeare/SimpleITK,blowekamp/SimpleITK,SimpleITK/SimpleITK,InsightSoftwareConsortium/SimpleITK,blowekamp/SimpleITK,InsightSoftwareConsortium/SimpleITK,kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix,InsightSoftwareConsortium/SimpleITK,SimpleITK/SimpleITK,SimpleITK/SimpleITK,SimpleITK/SimpleITK,InsightSoftwareConsortium/SimpleITK,richardbeare/SimpleITK,richardbeare/SimpleITK,richardbeare/SimpleITK,blowekamp/SimpleITK,InsightSoftwareConsortium/SimpleITK,SimpleITK/SimpleITK,InsightSoftwareConsortium/SimpleITK,SimpleITK/SimpleITK,kaspermarstal/SimpleElastix,blowekamp/SimpleITK,SimpleITK/SimpleITK,SimpleITK/SimpleITK,blowekamp/SimpleITK,blowekamp/SimpleITK,richardbeare/SimpleITK,InsightSoftwareConsortium/SimpleITK,richardbeare/SimpleITK,kaspermarstal/SimpleElastix,InsightSoftwareConsortium/SimpleITK,kaspermarstal/SimpleElastix,richardbeare/SimpleITK