Bump LLVM to 5.0.0
Bump LLVM to 5.0.0

Also bump CastXML to address Visual Studio build output consistency addressed
in CastXML/CastXML@3a81f3cc3060be86064ba2e666d30b0c358cc847

CastXML/CastXMLSuperbuild,thewtex/CastXMLSuperbuild