When deciding whether or not to resolve two

When deciding whether or not to resolve two
anonymous structs to the same Decl in the
ASTImporter, ensure that both are filled in
from their external sources (if present).
Otherwise two different structs may be
identified erroneously.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@202869 91177308-0d34-0410-b5e6-96231b3b80d8