Objective-C: Removes a bogus warning about auto-synthesis
of properties. Fixes // rdar://14085456


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@183542 91177308-0d34-0410-b5e6-96231b3b80d8
Define id to the correct type.

Found this while working on pr16247. The fix for that bug will cause clang to
reject this.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@183545 91177308-0d34-0410-b5e6-96231b3b80d8