Update clang to r339409.

Change-Id: I800772d2d838223be1f6b40d490c4591b937fca2
diff --git a/linux-x64/clang/include/llvm/Support/ConvertUTF.h b/linux-x64/clang/include/llvm/Support/ConvertUTF.h
index 99ae171..6ae56c2 100644
--- a/linux-x64/clang/include/llvm/Support/ConvertUTF.h
+++ b/linux-x64/clang/include/llvm/Support/ConvertUTF.h
@@ -92,6 +92,7 @@
 
 #include <cstddef>
 #include <string>
+#include <system_error>
 
 // Wrap everything in namespace llvm so that programs can link with llvm and
 // their own version of the unicode libraries.
@@ -286,6 +287,21 @@
 bool convertUTF8ToUTF16String(StringRef SrcUTF8,
                               SmallVectorImpl<UTF16> &DstUTF16);
 
+#if defined(_WIN32)
+namespace sys {
+namespace windows {
+std::error_code UTF8ToUTF16(StringRef utf8, SmallVectorImpl<wchar_t> &utf16);
+/// Convert to UTF16 from the current code page used in the system
+std::error_code CurCPToUTF16(StringRef utf8, SmallVectorImpl<wchar_t> &utf16);
+std::error_code UTF16ToUTF8(const wchar_t *utf16, size_t utf16_len,
+                            SmallVectorImpl<char> &utf8);
+/// Convert from UTF16 to the current code page used in the system
+std::error_code UTF16ToCurCP(const wchar_t *utf16, size_t utf16_len,
+                             SmallVectorImpl<char> &utf8);
+} // namespace windows
+} // namespace sys
+#endif
+
 } /* end namespace llvm */
 
 #endif