More improvements to namespace aliases. We now support everything except aliases in using directives.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@67966 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/Sema.h b/lib/Sema/Sema.h
index ab1e9d4..0ebccf3 100644
--- a/lib/Sema/Sema.h
+++ b/lib/Sema/Sema.h
@@ -970,7 +970,7 @@
       return isa<TypedefDecl>(D) || D->isInIdentifierNamespace(Decl::IDNS_Tag);
       
     case Sema::LookupNamespaceName:
-      return isa<NamespaceDecl>(D);
+      return isa<NamespaceDecl>(D) || isa<NamespaceAliasDecl>(D);
     }
     
     assert(false &&