[arcmt] Allow -retain of an __unsafe_unretained receiver if the result gets used.
Keep the error if the result is unused. rdar://9552694.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@135209 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed