Introduce a module import declaration, so that we properly represent, e.g.,

  __import_module__ std.vector;

in the AST.

llvm-svn: 145725
diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index d892c56..f4507e3 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -501,6 +501,7 @@
     case ObjCImplementation:
     case ObjCCategory:
     case ObjCCategoryImpl:
+    case Import:
       // Never looked up by name.
       return 0;
   }