Fix a crash-on-invalid when parsing a reference to an invalid auto declaration

  auto x((unknown));
  int& y = x;

would crash because we were not flagging 'x' as an invalid declaration here.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@165675 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed