Bitcode: Add `OLD_` prefix to metadata node records

I'm about to change these, so move the old ones out of the way.

Part of PR21532.

llvm-svn: 224070
diff --git a/llvm/tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp b/llvm/tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp
index f95b272..a186659 100644
--- a/llvm/tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp
+++ b/llvm/tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp
@@ -266,8 +266,8 @@
     case bitc::METADATA_STRING:      return "METADATA_STRING";
     case bitc::METADATA_NAME:        return "METADATA_NAME";
     case bitc::METADATA_KIND:        return "METADATA_KIND";
-    case bitc::METADATA_NODE:        return "METADATA_NODE";
-    case bitc::METADATA_FN_NODE:     return "METADATA_FN_NODE";
+    case bitc::METADATA_OLD_NODE:    return "METADATA_OLD_NODE";
+    case bitc::METADATA_OLD_FN_NODE: return "METADATA_OLD_FN_NODE";
     case bitc::METADATA_NAMED_NODE:  return "METADATA_NAMED_NODE";
     }
   case bitc::USELIST_BLOCK_ID: