MS ABI: Don't be so hasty to judge an inheritance model

If we are in the middle of defining the class, don't attempt to
validate previously annotated declarations.  We may not have seen base
specifiers or virtual method declarations yet.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@200959 91177308-0d34-0410-b5e6-96231b3b80d8