Update clang to r339409.

Change-Id: I800772d2d838223be1f6b40d490c4591b937fca2
diff --git a/linux-x64/clang/include/llvm/ADT/None.h b/linux-x64/clang/include/llvm/ADT/None.h
index c7a99c6..4b6bc1e 100644
--- a/linux-x64/clang/include/llvm/ADT/None.h
+++ b/linux-x64/clang/include/llvm/ADT/None.h
@@ -17,7 +17,7 @@
 #define LLVM_ADT_NONE_H
 
 namespace llvm {
-/// \brief A simple null object to allow implicit construction of Optional<T>
+/// A simple null object to allow implicit construction of Optional<T>
 /// and similar types without having to spell out the specialization's name.
 // (constant value 1 in an attempt to workaround MSVC build issue... )
 enum class NoneType { None = 1 };