Make CXXScopeSpec invalid when incomplete, and propagate that into any
Declarator that depends on it.  This fixes several redundant errors and bad
recoveries.

llvm-svn: 100779
diff --git a/clang/lib/Frontend/PrintParserCallbacks.cpp b/clang/lib/Frontend/PrintParserCallbacks.cpp
index 8d64a64..9d4600f 100644
--- a/clang/lib/Frontend/PrintParserCallbacks.cpp
+++ b/clang/lib/Frontend/PrintParserCallbacks.cpp
@@ -197,7 +197,7 @@
     }
 
     virtual DeclPtrTy ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK,
-                               SourceLocation KWLoc, const CXXScopeSpec &SS,
+                               SourceLocation KWLoc, CXXScopeSpec &SS,
                                IdentifierInfo *Name, SourceLocation NameLoc,
                                AttributeList *Attr, AccessSpecifier AS,
                                MultiTemplateParamsArg TemplateParameterLists,