Update clang to r339409.

Change-Id: I800772d2d838223be1f6b40d490c4591b937fca2
diff --git a/linux-x64/clang/include/llvm/Support/ThreadLocal.h b/linux-x64/clang/include/llvm/Support/ThreadLocal.h
index 427a67e..885bd18 100644
--- a/linux-x64/clang/include/llvm/Support/ThreadLocal.h
+++ b/linux-x64/clang/include/llvm/Support/ThreadLocal.h
@@ -24,7 +24,7 @@
     // YOU SHOULD NEVER USE THIS DIRECTLY.
     class ThreadLocalImpl {
       typedef uint64_t ThreadLocalDataTy;
-      /// \brief Platform-specific thread local data.
+      /// Platform-specific thread local data.
       ///
       /// This is embedded in the class and we avoid malloc'ing/free'ing it,
       /// to make this class more safe for use along with CrashRecoveryContext.