Objective-C ARC. Provide diagnostic and fix-it 
when casting a retainable object to a objc_bridge_related
CF type with the suggestion of applying the method
specified in the bridging attribute to the object.
// rdar://15932435


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@211807 91177308-0d34-0410-b5e6-96231b3b80d8