Move the creation of the record type for the state of Objective-C fast

enumerations from the ASTContext into CodeGen, so that we don't need
to serialize it to AST files. This appears to be the last of the
low-hanging fruit for SpecialTypes.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@137124 91177308-0d34-0410-b5e6-96231b3b80d8