Objective-C. Consider block pointer as NSObject as well as conforming to
'NSCopying' protocol when diagnosing block to ObjC pointer conversion.
// rdar://16739120


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@210491 91177308-0d34-0410-b5e6-96231b3b80d8