BUG: Update Superbuild SWIG to 2.0.4.
BUG: Update Superbuild SWIG to 2.0.4.

Fixes build on gcc-4.6 because of ptrdiff_t errors.

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