Explicitly handle LinkOnceODRAutoHideLinkage. NFC. We already have a test.

llvm-svn: 225449
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 3dc3b7e..7c7eebd 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -133,6 +133,8 @@
     return GlobalValue::PrivateLinkage; // Obsolete LinkerPrivateLinkage
   case 14:
     return GlobalValue::PrivateLinkage; // Obsolete LinkerPrivateWeakLinkage
+  case 15:
+    return GlobalValue::ExternalLinkage; // Obsolete LinkOnceODRAutoHideLinkage
   }
 }