Header guard canonicalization, clang part.

Modifications made by clang-tidy with minor tweaks.

llvm-svn: 215557
diff --git a/clang/lib/Index/SimpleFormatContext.h b/clang/lib/Index/SimpleFormatContext.h
index a460863..286d976 100644
--- a/clang/lib/Index/SimpleFormatContext.h
+++ b/clang/lib/Index/SimpleFormatContext.h
@@ -13,8 +13,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_CLANG_SIMPLE_FORM_CONTEXT_H
-#define LLVM_CLANG_SIMPLE_FORM_CONTEXT_H
+#ifndef LLVM_CLANG_LIB_INDEX_SIMPLEFORMATCONTEXT_H
+#define LLVM_CLANG_LIB_INDEX_SIMPLEFORMATCONTEXT_H
 
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/DiagnosticOptions.h"