Apart from storing/retrieving the previous redeclaration from PCH, also store/retrieve the most recent
redeclaration. That way we are sure that the full redeclarations chain is loaded.

When using chained PCHs, first declarations point to the most recent redeclarations in the same PCH.
To address this use a REDECLS_UPDATE_LATEST record block to keep track of which first declarations need
to point to a most recent redeclaration in another PCH.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@110125 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/Frontend/PCHBitCodes.h b/include/clang/Frontend/PCHBitCodes.h
index 109a78b..a07060f 100644
--- a/include/clang/Frontend/PCHBitCodes.h
+++ b/include/clang/Frontend/PCHBitCodes.h
@@ -245,8 +245,12 @@
       /// declarations.
       TU_UPDATE_LEXICAL = 28,
 
+      /// \brief Record code for an update to first decls pointing to the
+      /// latest redeclarations.
+      REDECLS_UPDATE_LATEST = 29,
+
       /// \brief Record code for declarations that Sema keeps references of.
-      SEMA_DECL_REFS = 29
+      SEMA_DECL_REFS = 30
     };
 
     /// \brief Record types used within a source manager block.