When completing Objective-C instance method invocations, perform a contextual conversion to an Objective-C pointer type of the target expression if needed. This fixes code completion of method invocations where the target is a smart pointer that has an explicit conversion operator to an Objective-C type.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@202529 91177308-0d34-0410-b5e6-96231b3b80d8