In debugger support mode, if we have a top-level message send

expression with an unknown result type, assume that the result type is
'id'. Fixes <rdar://problem/10400663>.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@146622 91177308-0d34-0410-b5e6-96231b3b80d8