Update clang to r339409.

Change-Id: I800772d2d838223be1f6b40d490c4591b937fca2
diff --git a/linux-x64/clang/include/llvm/BinaryFormat/Dwarf.h b/linux-x64/clang/include/llvm/BinaryFormat/Dwarf.h
index 15724a9..9036f40 100644
--- a/linux-x64/clang/include/llvm/BinaryFormat/Dwarf.h
+++ b/linux-x64/clang/include/llvm/BinaryFormat/Dwarf.h
@@ -540,6 +540,10 @@
 /// for attribute Attr.
 StringRef AttributeValueString(uint16_t Attr, unsigned Val);
 
+/// Returns the symbolic string representing Val when used as a value
+/// for atom Atom.
+StringRef AtomValueString(uint16_t Atom, unsigned Val);
+
 /// Describes an entry of the various gnu_pub* debug sections.
 ///
 /// The gnu_pub* kind looks like: