Objective-C: Provide fixit suggestions when class object
is accessed via accessing 'isa' ivar to use
object_getClass/object_setClass apis.
// rdar://13503456


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178282 91177308-0d34-0410-b5e6-96231b3b80d8