Update clang to r339409b.

Change-Id: Ied8a188bb072c40035320acedc86164b66d920af
diff --git a/linux-x64/clang/include/clang-c/Index.h b/linux-x64/clang/include/clang-c/Index.h
index 86383d1..56b510d 100644
--- a/linux-x64/clang/include/clang-c/Index.h
+++ b/linux-x64/clang/include/clang-c/Index.h
@@ -5606,9 +5606,14 @@
   CXCompletionContext_NaturalLanguage = 1 << 21,
 
   /**
+   * #include file completions should be included in the results.
+   */
+  CXCompletionContext_IncludedFile = 1 << 22,
+
+  /**
    * The current context is unknown, so set all contexts.
    */
-  CXCompletionContext_Unknown = ((1 << 22) - 1)
+  CXCompletionContext_Unknown = ((1 << 23) - 1)
 };
 
 /**