Update clang to r339409.

Change-Id: I800772d2d838223be1f6b40d490c4591b937fca2
diff --git a/linux-x64/clang/include/llvm/Support/xxhash.h b/linux-x64/clang/include/llvm/Support/xxhash.h
index f7ca460..6fd67ff 100644
--- a/linux-x64/clang/include/llvm/Support/xxhash.h
+++ b/linux-x64/clang/include/llvm/Support/xxhash.h
@@ -38,10 +38,12 @@
 #ifndef LLVM_SUPPORT_XXHASH_H
 #define LLVM_SUPPORT_XXHASH_H
 
+#include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/StringRef.h"
 
 namespace llvm {
 uint64_t xxHash64(llvm::StringRef Data);
+uint64_t xxHash64(llvm::ArrayRef<uint8_t> Data);
 }
 
 #endif