Add missing emacs major mode marker.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@166912 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/libclang/IndexingContext.h b/tools/libclang/IndexingContext.h
index 78a8abc..0fc7238 100644
--- a/tools/libclang/IndexingContext.h
+++ b/tools/libclang/IndexingContext.h
@@ -1,4 +1,4 @@
-//===- IndexingContext.h - Higher level API functions ------------------------===//
+//===- IndexingContext.h - Higher level API functions -----------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //