Specifying the diagnostic argument through the attribute table generator instead of having to enter it manually as part of the attribute subject list. This only affects attributes appertaining to ObjC interfaces and protocols.

No new tests required as this is covered by existing tests.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@213193 91177308-0d34-0410-b5e6-96231b3b80d8