Sort the #include lines for unittests/...

I've tried to place sensible headers at the top as main-module headers.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@169243 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/unittests/Format/FormatTest.cpp b/unittests/Format/FormatTest.cpp
index 9929eeb..bb24bb3 100644
--- a/unittests/Format/FormatTest.cpp
+++ b/unittests/Format/FormatTest.cpp
@@ -7,9 +7,9 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "clang/Format/Format.h"
 #include "../Tooling/RewriterTestContext.h"
 #include "clang/Lex/Lexer.h"
-#include "clang/Format/Format.h"
 #include "gtest/gtest.h"
 
 namespace clang {