Allow objc @() syntax for enum types.

Previously we would reject it as illegal using a value of
enum type and on ObjC++ it was illegal to use an enumerator
as well.

rdar://11454917

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@156843 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed