Sort the #include lines for unittests/...

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

llvm-svn: 169243
diff --git a/clang/unittests/Lex/PPCallbacksTest.cpp b/clang/unittests/Lex/PPCallbacksTest.cpp
index 02b374b..295fa40 100644
--- a/clang/unittests/Lex/PPCallbacksTest.cpp
+++ b/clang/unittests/Lex/PPCallbacksTest.cpp
@@ -7,6 +7,7 @@
 //
 //===--------------------------------------------------------------===//
 
+#include "clang/Lex/Preprocessor.h"
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/LangOptions.h"
@@ -16,12 +17,9 @@
 #include "clang/Lex/HeaderSearch.h"
 #include "clang/Lex/HeaderSearchOptions.h"
 #include "clang/Lex/ModuleLoader.h"
-#include "clang/Lex/Preprocessor.h"
 #include "clang/Lex/PreprocessorOptions.h"
-
 #include "llvm/ADT/SmallString.h"
 #include "llvm/Support/PathV2.h"
-
 #include "gtest/gtest.h"
 
 using namespace llvm;