Revert "[clang] Build UsingType for elaborated type specifiers."

This reverts commit e70ca7b35319a3621f9d9c6475926428f8c5c000 and the
followup patch "[clang] Fix the location of UsingTypeLoc"
(ebbeb164c25a40cb6ba9c6b18dce5dcd06c0bb07).

The patch causes an incorrect lookup result:

```
namespace ns { struct Foo { };}

using ns::Foo;
void test() {
  struct Foo {
  } k; // the type of k refers to ns::Foo, rather than the local Foo!
}
```

1 files changed, 5 insertions, 6 deletions

diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index c7fd115..e6812ac 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -4965,7 +4965,6 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
   bool IsDependent = false;
   const char *PrevSpec = nullptr;
   unsigned DiagID;
-  UsingShadowDecl* FoundUsing = nullptr;
   Decl *TagDecl =
       Actions.ActOnTag(getCurScope(), DeclSpec::TST_enum, TUK, StartLoc, SS,
                     Name, NameLoc, attrs, AS, DS.getModulePrivateSpecLoc(),
@@ -4974,7 +4973,7 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
                     BaseType, DSC == DeclSpecContext::DSC_type_specifier,
                     DSC == DeclSpecContext::DSC_template_param ||
                         DSC == DeclSpecContext::DSC_template_type_arg,
-                    OffsetOfState, FoundUsing, &SkipBody).get();
+                    OffsetOfState, &SkipBody).get();
 
   if (SkipBody.ShouldSkip) {
     assert(TUK == Sema::TUK_Definition && "can only skip a definition");
@@ -4984,8 +4983,8 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
     T.skipToEnd();
 
     if (DS.SetTypeSpecType(DeclSpec::TST_enum, StartLoc,
-                           NameLoc.isValid() ? NameLoc : StartLoc, PrevSpec,
-                           DiagID, FoundUsing ? FoundUsing : TagDecl, Owned,
+                           NameLoc.isValid() ? NameLoc : StartLoc,
+                           PrevSpec, DiagID, TagDecl, Owned,
                            Actions.getASTContext().getPrintingPolicy()))
       Diag(StartLoc, DiagID) << PrevSpec;
     return;
@@ -5039,8 +5038,8 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
   }
 
   if (DS.SetTypeSpecType(DeclSpec::TST_enum, StartLoc,
-                         NameLoc.isValid() ? NameLoc : StartLoc, PrevSpec,
-                         DiagID, FoundUsing ? FoundUsing : TagDecl, Owned,
+                         NameLoc.isValid() ? NameLoc : StartLoc,
+                         PrevSpec, DiagID, TagDecl, Owned,
                          Actions.getASTContext().getPrintingPolicy()))
     Diag(StartLoc, DiagID) << PrevSpec;
 }