Reapply "DebugInfo: Omit class definitions even in the presence of available_externally vtables"

Accounts for a case that caused an assertion failure by attempting to
query for the vtable linkage of a non-dynamic type.t

This reverts commit r292801.

llvm-svn: 293462
diff --git a/clang/lib/CodeGen/CGDebugInfo.h b/clang/lib/CodeGen/CGDebugInfo.h
index ac2e8dd..ea451d0 100644
--- a/clang/lib/CodeGen/CGDebugInfo.h
+++ b/clang/lib/CodeGen/CGDebugInfo.h
@@ -409,6 +409,7 @@
   void completeType(const RecordDecl *RD);
   void completeRequiredType(const RecordDecl *RD);
   void completeClassData(const RecordDecl *RD);
+  void completeClass(const RecordDecl *RD);
 
   void completeTemplateDefinition(const ClassTemplateSpecializationDecl &SD);