We were crashing whenever a C++ pointer-to-member was taken, that was pointing
to a member of an anonymous structure field within a class, eg.

  struct A {
    struct {
     int x;
    };
  };
  // ...
  &A::x;

Differential Revision: https://reviews.llvm.org/D39800


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@319055 91177308-0d34-0410-b5e6-96231b3b80d8